The problem is, without a feat like this some players would have just looked at the available PRC's and thought "that looks nice", ticked a few boxes and gone running around the server with their sparkling toons.
+1
I gladly made that sacrifice of a feat to be able to play that prc. It made it even feel more special from my perspective. Highly subjective though, I know.
No chance that playing a cleric or paladin or whoever is supposed to be a true believer without that feat will give me, again.. just me, the feeling that this sacrifice of a feat did.
I don't know about all the features of those prcs that requires it but I feel that mine pays back that loss greatly.
Judging from this I cannot see why this is useless, a too great loss nor does it really require to be of at least little use other than it is already.
Something like a will +2 is yet another advantage for already powerful prcs.
.....
After unloading all these thoughts it seems to be much of a matter of taste. Some like it, some do not. I can see a balancing purpose behind it.. I can see a purpose that these prcs require it..
As much as the lore is ignored already (( nowadays?? )) I really appreciate some difficulties on the way to build a toon. Infact I would vote for far more applications for races and and builds. But this is just me and I am far from being perfect.