I'm not sure you're going to find one unifying answer, so I'll just contribute my own experience. - FreeBSD lost the desktop battle to Linux. All joking aside about Linux on the desktop, if you want a *nix environment (and not Mac), Linux distributions are just a lot easier to set up and have traditionally enjoyed better packaging of proprietary software (graphics card drivers, RAID card drivers, applications, etc.).…
Heck even Apple dont use FreeBSD with their Servers