If no one answers my questions, why can't I have the points for a bounty returned?
If someone offers a reward and no one cashes in, the person doesn't forfeit the amount.
So what is the deal?
The main FAQ entry about bounties covers this, and there are a few existing meta questions on it:
The best explanation is probably from the FAQ entry:
What happens if there's no answer after the bounty period?
If after the end of the bounty period a question has no answers, no bounty will be awarded and the question will no longer be featured.
Bounties are best understood as exchanging reputation for higher question visibility and increased answerer motivation. A bounty does not guarantee a response and is not refunded if none are received.
As an answer on one of the other posts points out, if you got the rep back you'd be able to immediately start another bounty -- you could keep your question on the Featured list forever (until it gets an answer, anyway), and if a bunch of people start doing that it makes bounties less useful for everyone. You're paying for extra exposure, not the answer itself, although hopefully the former leads to the latter