Implying a separation just because there are different ways is at best inconsiderately.
From the same point of view I could ask you why do you separate from your neighbour, because of not having the same furniture, driving the same car, wearing the same clothes, cheer for the same team... - having the same live-style, while certainly there are points you could improve by doing it like your neighbour.
You could also ask why Linux is not becoming more BSD.
Doing things differently is not only some kind of freedom but the most important part of evolution.
Both worlds are not separated that strictly.
Besides there are not a few developers working in both worlds, at least the whole universe of OpenSource is overlapping, which makes most of what the user eventually needs for its daily usage.
To put it in a nutshell:
If most of what you do on a computer is e.g. using firefox, LibreOffice, and VLC, it doesn't really matter much, which system is below.
Several Linux-distros offer fully automatic installation and configuration of everything.
Downside: You have to stick with what others have chosen.
If you don't like that, such as me and many others, but want your own personal, individually tailored system - one does not need to create "a new distro for everybody" again, then you need something modular, like FreeBSD.
Downside: Your effort is needed. Nobody else can read your mind, and deliver you your system as you want to be it exactly - except youself.
And besides that, both worlds look and learn from each other.
Not only the things could be done better, but at least important also to avoid the mistakes, the others did.
It's not up to FreeBSD if Linux implements ZFS (which they are doing.)
And in anyway anything has to fit the concept.
In my eyes that's a core difference of BSD and Linux - the concept of how things have to be done.
In my eyes in Linux-universe there is either the total open, less restrictive, more easy, loose way to do things, a creative playground, which produces masses of software-packages - but also lots of junk and useless crap,
or there are those projects under the lead of some "dictatorhip" - those produce the functioning turn-key-distris; which came a
long way to get there, baby - a long way.
Trying to install some Red-Hat-Linux in the late 90s from several diskettes, getting an X-server up and running on those tube-monitors, fumbling hours only with mode-lines on a flickering, distorted screen (if any), and such adventures, are war stories nobody today believes anymore who doesn't made those experiences himself.
And those who did for sure don't want to get back there again.
I fumbled a lot with many Linux many years.
All this "sudo apt get...", "sudo apt foo...", "sudo apt bar..." (just to mention one of today's Linux-installation methods), just for getting "Error... error... error... Aborted!" (almost Everytime, with
any Linux-Installation tool) really pissed me.
To me an OS is not for to end in itself, install it, tinker with updates, handling errors, being happy when finally something simply runs, and waiting impatiently for the new version to come just to have again something to tinker with.
I want/need to
use the software.
System's administration is a necessary must, but not the purpose for a computer, which by the way is not just a personal opinion.
The first time on FreeBSD I did a
pkg install ...
or a
make install ...
within ports tree, and the shit simply ran from the start until the very end without any complains, no aborting errors, simply produced an then installed, and working piece of software at the very first go - and it worked reliably everytime.
That's what sold me FreeBSD.
This for me is for certain a crucial point I definitely do not want "more Linux" in FreeBSD.
Absolutely not! For sure not in this point. No discussions, not compromises. No!
It's not "old-school old-farts are not capable of changing anymore", it's simply the experience not to get back into the moisty trenches, again.
Linux-universe is full of people having lots of fancy ideas.
But that's not the first things one needs.
Even if many are not agreeing with me, not willing it to understand, especially not the ones with fancy ideas,
but the crucial point of the famous journey over a thousand miles that starts with the famous first step is it will not reach a destination if the thousand miles are not traveled until its end.
It doesn't matter if it's an OS, an airplane, or a simple craft kit: The most important thing is, the job needs to be done in full. Otherwise you end up with some partially-finished mess "to be continued someday", stored away in the attic. Linux-universe has a large attic of such things.
The more comprehensive, and the more complex a system becomes, the more people are needed.
The more people are involved, the more organization becomes vital.
Something many do not accept. Especially the "creative ones" sense it as an offensive, ideas-killing-environment, feeling restricted in their liberty, and start looking elsewhere for "more freedom", for more understanding for their ingenious ideas, running from pillar to post, instead to learn that work most of the time is tedious, and simply has to be done. And not by others, only.
To get something reliable one need reliable people, finishing tedious work reliably on time.
For that organisation is needed. Way -
way - more than fancy ideas.
Which means less liberty, but more efficient usage of resources, and reliable success.
It's the very nature, the whole point of organization, to define what has to be done, and what not.
Of course, one may discuss how organization is to be done -
before you start.
But then one has to decide for and stick to it, and if so do the job. Or beat it,
before.
Discussions about organization while a running project over and over again is mostly just another way to simulate effort, while bringing in new, fancy ideas again, instead of doing real work, while using up resources needed for doing the work.
Again, not old-fart's paranoia but simply real-life experience.
When the work is done, and resources are left, then one may start to realize new ideas.
Anything else will sooner or later only end up in the attic.
I could think of is the license difference, but that doesn't seem a very big snag.
If you are a private user, doing only private things for personal use, then you don't need to bother about if the software you're using is under GPL, MIT, Apache, or BSD license.
But if you want to spread your work to others, especially to be used by others, or even do something professional, particulary want to earn money with it, then you better take a very good and close look at licenses, because especially the GPL contains dangerous traps you may naivly run into, may shut your project down, cost you money, or both.
Besides that you cannot simple discriminate "Linux = GPL, FreeBSD = BSD license" - which is true for the very system (Linux: the kernel) - but that's not all a system consists of.
The makers decide under which license they publish their software.
So you'll find all kind of OpenSource lincenses in both worlds.
Examples:
Gimp is under GPL; doesn't matter if you run it under Linux, or BSD.
So is gcc.
clang is Apache, no matter if it's under BSD or Linux.
So if you're not want to do anything for personal, private use, only, anymore, you better take a good look at all the software that is involved in your process, at each of its licenses, and potentielly contact the license owner, or change to some other piece of software.