Shouldnt people use more their reputation points for Bounties?
and is there some statistics available about this vs other stackexchange sites?
Hard to say that they should, but the use of bounty is documented in the faq:
In general you would institute a bounty when you aren't getting answers, or you are getting inadequate answers.
As far as use on the network, it scales with traffic; you can browse around and check the homepage of a few sites in the Stack Exchange network:
... and look for the Featured tab; if there are no bountied questions, this tab will not be present at all. But if it is, there will be a small number counting the # of bountied questions at the moment.
I'm not sure bounties would work for a Quant SE. For programming, you get a simple question-answer form, and to get an answer to a difficult question, you pay with rep points. On Quant SE, I'm not sure the same would work, mainly because questions are a lot more subjective.