Why do you think that those who ask questions on Answers let it go to voting?

I realize that some people can't decide on a best answer, so they let voters decide; but I think there can be other reasons why they don't vote on a best answer. Is it often because they don't know how to vote on best answer (I see a lot of people asking how to do this)? Or, is it because they didn't like any of the answers and don't know that they can just choose "No best answer"? Or is it just because they forgot to vote in time and didn't check their email to know the 4 days was up? The reason I'm asking is, I tend to think that a lot of people may be kind of unappreciative of the answers and they don't think the answerers need any feedback. I mean, they might be taking our advice, but then they don't bother to say a simple thank you and vote our answer as the best one. What do you think? Are people just lazy, inconsiderate, forgetful, or inexperienced with how to vote?