Airdrops were so popular among the crypto-community over the years. One of the key features of the airdrops is, it gives every participant a chance to get some free tokens by completing few tasks. Most importantly it is totally free of charge.
Yes, airdrop are very worthy back then, 2017 was the time that they are really that good, I remember the Onion airdrop and it was one of the biggest and hottest airdrop then.
But nowadays we frequently see a trend where the organizers of some of the airdrops ask to send a small fee prior to sending the tokens. In some cases, they put a condition saying that in order to withdraw tokens or any fund received from the sale of tokens, it is mandatory to take part in their ICOs. I would rather call such events as "Scam-drops" as they not only dilute the meaning of airdrops, but also make people to move away from future events due to lack of trust.
I think this started in 2018, when their is a airdrop boom, but projects or scammers behind the project will ask you for a certain fee, worst will ask you your privatekey before they can airdrop you that worthless token. Lol, very tricky indeed. And then there are projects that will ask you a complete KYC procedure first, also very shady.