Recently there was some discussion (in comments to some questions and in chat) about:
accepting answers and unwillingness of some users to do so;
some users find comments reminding users to improve their acceptance rate a little annoying.
I think it would be good to have collected in one place some arguments why it is important to accept an answer, if at least one good answer is given. And, perhaps, if someone feels strongly about why he is not accepting answers, some explanations about this could be given here, too. (At least, meta is certainly a better place to discuss this than comments and chat.)
See also: How to accept an answer