> The difference is that with the BSDs everyone can take and don't bother to contribute upstream, e.g. Apple and Sony.
This depends on the use case of the company.
A lot of companies learned that simply forking the project and not giving back is a good pathway to pain because now you have to carry your internal patches forward, as well as a larger and larger diff against the base OS itself as it changes.
If you forked (e.g.) FreeBSD 9 and based your product off of it, and the project is now at version 12.x (with 13.x in 2021Q1), then that's a lot to keep up with internally.
It's better to use the base OS, and the documented APIs, for one's secret sauce, and give back everything else. This is what vendors like Netflix, Dell-EMC Isilon, NetApp, etc. do. You'll also see quite a few patches from Microsoft and Amazon as they want to sell their cloud services for as many guest OSes as possible. Hardware vendors (Chelsio, Mellanox, Cavium) also throw in support so that hardware companies will use their products with-in appliances.
Others, like Sony with the PS4 and PS5, mostly seem to operate in user land and so do not do much kernel-level stuff (except perhaps booting code) that would need to be back ported.
Probably because they don't care with stay current: the PS4 isn't going to change much after initial development, so why should the base OS? Similarly now that the PS5 has shipped, I doubt there will be much OS development there.
If FreeBSD (or Linux) weren't around, then they'd simply purchase/license an embedded OS (QNX?) and use that.
Isn't that argument put to bed by the fact that all of the BSDs still exist, are actively maintained including new features and are used by many individuals/corps in a diverse range of cases?
There is hardly a reason to install them other than wanting free beer OS without GPL-strings attached or being a systemd hater, and then suffer a desktop experiece that feels like stuck in early 2000.
Conferences related to BSDs usually boil down to running the same code in newer hardware or filesystems.