As others have mentioned, it is incredibly frustrating to answer a question and then never have the asker accept any of the responses as the answer.
It's not only frustrating as someone who likes to help by answering questions even if there's already discussion going on, but it often causes the wrong answers to show up first/sooner in search results.
There don't seem to be any hats this year for accepting answers.
I can personally attest that Winter Bash hats have already incentivized me; I want to earn more hats, they're adorable! But then the same frustration arises as before with un-accepted answers...it's a rather annoying cycle that keeps me (and I would bet others) from participating to the fullest.
Are hats for accepting something we can hope for, or are there reasons it would be a horrible idea?