I'm quite sure most of them are scam, and you surely chose the bad ones to participate.

But I also think there were ways that could have helped you to avoid wasting your time.
First of all, evaluate any project proposal before diving into it. And second, make sure that the developer of such project is using methods that prevent users of creating multiple accounts/wallets and having their gains based on it.

Byteball is an example of a successful airdrop, since the project proposal is quite solid, and the airdrop was based on the Bitcoin balances of its participants. You can still get Bytes, but right now it requires an ID verification.