Well, poorhouse is one of those things which will really shine when you hit its niche - a treasureless engine. I agree that it would be pretty useless outside of that. But four poorhouses is all you need for consistent double-province turns.
And since it costs 1, four poorhouses is actually a reasonable number to get. Sure, four Harvests can get you double-province, but you have to use four $5 hands to get it.
Open Workers Village/Chapel, you'll have a deck with three WV, four poor houses, and one chapel in no time at all. If you open, like, Remake/Steward in a game with a village on the board, that'll also get you there super-fast.
...actually, in general, I think that the presence of Poorhouse and some sub-$5 village is going to encourage faking a chapel opening - opening with two weaker trashers if chapel isn't around. Remake/Steward. Moneylender/Steward.