At least originally, it was because of the license.
BSDs unwavering commitment to reliability. A Linux kernel crashes. A lot. FreeBSD ran cdrom.com for 365+ days without rebooting. Just saying
What's "a lot" here, and are you sure that's still true? Because my suspicion is that it might have been true before FAANG sunk billons of R&D into Linux, but I would be shocked if Linux kernels cash at any rare worth noticing today. Although it's splitting hairs, really; when is the last time you saw any major kernel crash?
I crash FreeBSD every day :)
you're making me want to start building some BSD boxes
Every year I still see a Linux system or two live-lock. When I was still doing Solaris and FreeBSD admining that never happened.
However most systems aren't pushed to extremes, so these corner cases aren't seen very often, regardless of OS.
Reminder: Facebook tried to run the WhatsApp stack on Linux but they kept having kernel panics
I've got Linux servers that have gone that long without rebooting (and some that are much longer!), but I generally view it as a bad thing and a failing on my part, and would feel the exact same way if I was still running illumos and freebsd servers. Software updates happen for a reason, even on BSD, and servers running for that long mean that they aren't getting those updates.