Not all airdrops are easy and profitable. Some require you to do some social media announcements or tasks which consume a lot of time. Most of the times you register for an airdrop and coins never shows up.

Not all of them are like that though. I have seen people making money of airdrops alone. You need to be dedicated and should be able to spend quite a bit of time. Bounties are more beneficial in my opinion if you have the skills.