B doesn't really give any evidence at all, and the resulting uncertainty is creepy/awkward/uncomfortable. It makes women uneasy, because they aren't sure of his intentions. If they knew he liked them, they might be able to update him on whether or not they do. If they knew he didn't, then they could relax. But not knowing sucks.

Oddly, I have exactly this complaint from the other end; I want to condition my actions on whether or not a woman has any interest (show some myself if so, otherwise leave her alone) but can't correctly evaluate the conditional unless it's made explicit, which no one ever does.