This has become a thing since erc20 tokens got popular.
I feel like it would be more suitable to say "99% of token airdrops are scams".
(of course there will be scams outside of the whole token airdrop scene as well, but I'd bet my money on it that the amount of scams with tokens is abundantly bigger)

Those tokens are too easy to create and were always almost instantly tradeable on etherdelta.
Mix in an airdrop to get a community going and start dumping, before you have ever put in any dev work at all.