Why do people ask questions when they are not sure of their ability to figure out the Best Answer?

Or do not get the answers they were looking for? Either which way, when a question is put to vote, it can only mean the Asker has walked away for some reason. Is this right or have I got it all wrong? Need inputs to figure out the rationale behind Voting. No intention to criticize any Askers; I may very well be faced with this situation and so need clarity before I reach there.