I actually I start getting some random tokens to my ethereum wallet, even without applying for their airdropps. I think it can be considered some type of advertising, as after getting the token, the user will research what is that weird thing he got for free and if the project is interesting enough maybe he will join and stay for longer. However, I wonder how do they check which wallets are active, because they could basically send these tokens to dead and random wallets and I for sure haven't applied for any free coins.