At least for me, being able to use Linux as daily driver on my desktop was instrumental at making me more proficient. At that point using it in the server became natural. Nothing beats the exercise of being able to use the same environment for everyday computing and for running "serious" services.
I guess a good desktop experience has the same utility to the freebsd ecosystem.
I've had the same experience. Used FreeBSD as a server OS long enough to switch to it as my main desktop OS. In return I've learned a lot more that has made server administration better.
Companies started to use Windows NT servers in the 90s maybe because they cost less than UNIX servers from HP, IBM, Sun etc but also because they had a lot of technical staff which only knew Windows.
I guess a good desktop experience has the same utility to the freebsd ecosystem.