I noticed most people will read most questions anyway, hence posting a bounty is completely useless: if someone had an answer, they likely would have already given it.
Do you agree?
Does anyone have an idea on what to do about that?
When I have a question that needs answering and it doesn't appear to be getting any attention, I personally share it through Reddit. It usually brings enough exposure to the question to get it answered.
As for bounties, I do agree that at the time they generally don't do much to help promoting a question. However, they can also be used to thank someone for a really good answer. While I also had the same problem as you described - posting a bounty and nobody answering the question - I don't really see it as much of a problem. It's just another tool that will have its usefulness at certain situations in the future.