Why don't people accept an answer when they award the bounty?

Question

A lot of the answers that I have seen only have the bounty award but not the accepted mark. I have so far only see one that had both, until then I just thought that if it is a bounty then the winner of the bounty is the same as being accepted.

I can see the reason for separating them, that is not my question though.

I can only think of a few reasons and I was hoping you all would know the answer.

1. The OP didn't realize they were able to accept and grant award (accept and award process is confusing).
2. The OP forgot to accept it.
3. The bounty was offered and granted by a third party and the OP didn't accept it even though the third party awarded.
4. The OP thought it was a good answer and deserved the award but didn't really answer their question.

Answer 1

Why don't people accept an answer when they award the bounty?

One most probable reason could be that no one gave an answer which solved OP's problem (or there was no answer worthy of being accepted). There are situations where there is no straight forward solution so people provide alternates or workarounds. Now OP may decide not to accept any answer and he/she may not award the bounty to any of the answers. However, the system may automatically award the bounty after the grace period is over (provided that an answer has a score of 2).