Most need to do it to prevent scammers. If you're doing with a project that hasn't launched already, it's probably a scam.

I know that Hydro is doing a bounty right now which apparently can be completed in around 5 minutes. I've been in their community since the initial airdrop last year. Hydro was also the most profitable airdrop of 2018 too. Definitely might be one to check out: https://projecthydro.org/blog/hydro-pay-and-liquid-exchange-rewards-campaign/