But why don't you find those beautiful airdrops once, whose only request was to communicate an address to receive the gift?

Those olden golden days are gone for ever. Nowadays these airdrops are just for advertising purpose and nobody will benefit out of it. Not even projects are really benefitting out of those wasteful airdrops.
Nowadays almost all airdrops have no valid advantage. when I see especially airdrop from ICO or IEO tokens only become decoration on our wallet. so that I myself have never benefited from following the airdrop all this time which I have been working on