airdrop is meaningless. and it is used by these useless projects to get newbies to pay them a small attention for a while during the time when they are pumping the coin. otherwise there is no reason to give away money like that to get people to get in.
additionally airdrop is a method of distributing the supply for those coins/tokens that have 100% premine.

the early days of bitcoin was Satoshi mining bitcoin and some others like Hal Finey running a node and also mining bitcoin. then people saw the "idea" and got interested and started joining in little by little.
the pizza story that was mentioned above was years after that.