Well, I thought about trying to argue that it's better to keep polls awkward and ugly, so that people get discouraged from creating the darned things and just ask questions instead. :) But, in fact, you're right: You've tried that already, and it hasn't worked.

I suppose polls are the online equivalent of asking people in the audience to raise their hands. It's a similarly useless technique for actually gathering data, but it can be effective as a rhetorical tool. And, given that the alternative in an online forum is to write for a completely invisible audience, maybe it is sometimes better than nothing.