Isn't it better for people to choose an answer after awhile?
Should we add comments to questions advising people to please pick one?
It's not really appropriate to ask a user to accept an answer on a post. The system already has prompts in place to remind them to select an answer without having users commenting on every other post saying "you should accept an answer", "accept an answer", "please accept an answer" … it starts to look noisy and somewhat harassing.
Accepting an answer is an optional activity. Maybe the current answers haven't best helped that user, or maybe they don't want to accept an answer at all. That is perfectly okay. There is no need to press further.
For me I try when I can to accept answers, however often there is no great answer or there are a lot of partial answers that help an issue along, without really being comprehensive enough to be the accepted answer.
When I write an answer it is no big deal when it is not the accepted answer. If I have something to add that is not comprehensive I still like to add it without worrying about if it is the accepted answer.
Getting an answer that is the accepted answer is cool, but it is no big deal when you don't, its not a contest here, it is a place to get a question answered.
Having said that if this answer is not selected as the accepted answer, Frogs will rain down on the OP.