I see a lot of questions having sufficiently explanatory answers but the users still don't accept answers. Is this because of the fact that less frequent users are not familiar with the importance of accepting answers? What is the policy of Aviation.SE regarding this, to improve upon the current situation?
As you cannot go to other users' houses and force them to accept answers (I'm pretty sure that's a crime almost anywhere in the world), there is little to do for that except leaving a comment and remind the user to accept the most useful answer.
On the community side, one can upvote the useful answer(s) to be sure that if one does not get accepted, the most useful is still displayed on top.
I'm just going to add something that Federico said.
I might be considered one of your culprits. Looking at my profile, you will probably attack me from all corners as to why my very good questions, which contains incredibly up voted answers, are not accepted. My rationale for accepting is different, and may not sit well with many members of the community, but bear with me.
First, one questions with many answers, they can all outline different points. Instead of accepting one, I up vote those which I find helpful, and I don't accept anything because there is no single correct answer. In those which there is a good, or best answer, I accept. Otherwise, I simply up vote.
Yes, in cases like those, I'm better off to right an answer to include all points and accept it. I could make it community wiki too. And I know that I am a bit hypocritical in this sense (since I don't do this), but this would be the way to go. Time to start writing up things I guess. :)
Then, there are those questions where the answer doesn't satisfy the asker. For those who already know the answer, it could be an annoyance, but if I don't understand how an airplane flies yet, why should I say that I do?
For people that just "come and tell me", there isn't much we can do. But we will have the community deciding what to accept with the voting system.
There is an underlying issue here regarding the quest for points and badges. It is quite common to see people asking to have their answers accepted not because they firmly believe that such an answer, once accepted, will bring more good (read up Jeremy Bentham's utilitarianism).
If an answer is not accepted, move on. Competent, well versèd people will recognize a good answer by its content, smart people will be able to tell from the amount of upvotes the answer receives and diligent people will read the comments and conclude from there.
Stop begging the teacher to give you a gold star. Stop wanting the gold star, in the first place.