Since I am married, it has been many years that I have not had to be put in that situation, but when I was, it was just horrendous and I was ribbed by a sister for it too: uh, hey, Suzanne. Are you stupid or something? Can't you tell he fancies you? And she would laugh when I asked did she know?
I guess for me, it came down to not liking being me and thus, could not comprehend when a guy liked me and thus, the few times I did date, it was because they spelt it out for me and I was floored when they confessed!