questions are often asked before experimenting.
sometimes you find a solution.
currently you cant mark your own answer as correct.
it's been copied
here for example.
(btw can someone copy my answer, so I can mark it as correct) :D
On Stackoverflow this feature is also used to post findings you think other users might find useful. For example, if you run into an issue, solve that issue, and think that solution might be useful to others, you can post the question/answer so others can find it easily when they search the forum.
This would help show the community that there is a correct answer, even if it is from the same person that asked the question.