How is a bounty canceled when the person is asking for nonsensical details about a question that has been clearly asked and answered? Why do some RJ45 plugs have the lock release clip under a rubber cover? If the user is asking a question that isn't the same as the question in question, shouldn't they be required to formulate their own question?
When another user starts a bounty on an existing question they may think it already asked the question well enough to not have to create a duplicate or their own version. Bounties can be used to lure out other answers, or answers that address the note left by the bounty drop.
Only moderators can cancel a bounty.
If a user wants to throw a bounty onto something that has no reason to, that's their concern.
If the question needs to be migrated, a moderator will cancel the bounty before doing so.
If the question otherwise needs to be simply closed, the bounty may be either allowed to run out or cancelled immediately.