Answer this honestly, if you were asked to provide all of that info from random strangers, all for a grand total of like $10-$50 in bounties, would you willingly do it? And also figure about half the time the bounty would be completely worthless. I can't fathom why anyone would bother. It's not like the old days anymore when a bounty could be worth 1-2 btc.
If it is a project that I've researched thoroughly and believe it is worth it, yes, I would complete the KYC for that project. I've done it already a few times for a few projects, and these projects I invested in as well. I've had no regrets doing it either as they turned out to be as good of projects as I believed they would be based on my research.
But have you willingly given complete strangers all of your personal information, including a copy of your license or passport, plus utility bill, for $10? I'm not talking about ICOs or exchanges, or where there is a chance of making decent money. I mean bounties that usually pay barely anything. If yes, you are taking a greater risk than most. If no, that means you wouldn't even do your own campaign for free coins ... and that kind of answers your question why it's not exactly taking off.
If you have done cheapo bounties, then I'd recommend you re-evaluate your criteria there and consider the risk involved.
Forget if a project looks like it's worth it ... a zillion scams out there, and plenty have looked like decent projects. There is no way in the world I'd trust complete strangers here like that, no matter how fancy their website looked.
I hope you can at least understand where I am coming from. And why many feel a similar way. It's just too risky for most people. Now if doing the ICO thing, at least then some may take that risk. But nowadays most would prefer going for an IEO ... ICOs, unless from some well known company, probably isn't such a good idea. And you are asking for tips on a bounty campaign, not ICO, so KYC for an ICO is one thing (which I still dislike)... but KYC for a bounty seems ridiculous to a lot of people.
Anyway, I'll mention one other thing that bounty folks tend to like -- a real plan to get the coin on exchanges. So if the team can get the coin on an exchange while the campaign is ongoing, even if it's a smaller (yet not completely dinky) exchange, it's a plus.