There are some users who never accept any answers no matter how good the replies are. I am sure you all know that and it's not difficult to compile a list based on previous behaviors. What's even worse is that in many cases more than alternatives are offered as FULLY fledged answers to an OP and still the authors of an OP consistently continue not to care about accepting an answer.
And we are ACTUALLY discussing the press of a button. Nothing more difficult and/or tiring.
To me, this seems like a hit and run approach, i.e we ask, we get a reply and we care not for other users who could benefit.
Since it takes 5 votes to close a question, why doesn't it take 5 votes for an answer to be considered as accepted? Is there a good reason behind it? I think that if 5 people upvote an answer it should be enough to be considered an indication that a particular approach fully addresses all the issues of an OP.
Am I missing something?
Final comment: I know that one or more might raise the issue of an OP having multiple answers each with more than 5 votes. Again, all I am suggesting is an option that after 5 upvotes we can make an answer appear as accepted. So in situations like this one, the best answer would be chosen.
Edit 1: addressing the points by @rhermans
About the "5 votes" Nowhere in the OP is stated that things have to be done very quickly. I just pointed out that as closing questions is an act for good site maintenance so is having accepted answers to questions. That's all. To me there is a clear correlation.
Again, all I am suggesting is the possibility that after a week -for example- that answer(s) is(are) posted to a question, if the person who asked the question has not accepted any of those, we can judge that for ourselves. Pretty much the same situation with the closing of threads.
What is the problem we are trying to solve here? I never said that we should choose the most highly voted answer. All I said, is that it is bad that some users CONSISTENTLY ignore to press a button, even in cases in which the answers fully solve the question of the OP. If you think that it would be useful, I can give a non-exhaustive list of users behaving like that and we can discuss more concretely. And yes, my point was that since 5 of us can decide decide to close a question, it should also be possible that 5 of us can decide that a reply is a full answer. That's all. I think we can use our judgement.
Furthermore, it is questionable that only a single answer deserves to be considered an "Accepted" answer.
This is the system we already have. Only ONE answer can be the accepted answer. And there's no prohibition from going back and providing more answers to one question.
In my head, it's better to have a question with 5 replies and 1 to be chosen as accepted answer, than having a bulk of question with excellent answers none of which is marked as accepted. It's good site maintenance and helps new users navigate more easily.