I've only played around with bounties a couple of times.

I interpret them a little differently. I feel like it's the poster making it known that the answer is especially important to them and they'll zap a good answer much more than the normal amount.

We have several weekly contests that run regularly and could be bounties, but that's just not how they've been organized.

I agree with you, though, about feeling like bounties should be a bigger part of SN.