The number of questions that are not marked solved here is very high, IME. And the reason is, I believe, that the Mark As Answer function is an nondescript check mark in a circle. The number of questioners here with 1-1-1 karma is high, indicating that many of them are unfamiliar with this site’s intricacies. They simply don’t know how to, or even that they can or should, mark a good answer as such. Most of the “Answers”, it seems, have been marked so after the fact by regular members.
And so, the feedback is low, and that is not a good thing. Consequently a lot of the regulars here include a tag line instructing the questioners how to mark an answer. But that adds clutter and should not be necessary.
The answer is quite simple. The answer function needs a more prominent display, including accompanying text explaining how to mark an Answer.
I first thought to raise this issue at the bugs site, but there is no Website category that I could see, so here it is.