It's just because it's 4 way and I have bottom set on a straight-possible board (where all 3 opponents can easily hold T8, 99, and JJ)...so if there were ever a spot to fold a set, this 'could' be one of them.
So, obv, BB had
[8d], and btn (lol) had
[7c], a club hit the turn, and I didn't fill up...
PokerStove has me (against their actual hands) as 35.5% EV, so I actually did the right thing by calling. Also, I think that BB DOES have a combo hand here often enough (or an even worse hand) for this to be a call.