If you’re not paying for the product, you are the product. With doing an airdrop the project creates awareness about their ICO or token. It brings people to the project that otherwise would not have owned or heard about it. It could lead to token price appreciation, since people value a token they own higher than a token they don’t own. This is called the endowment effect.
Airdrops create a community/network of people who own the tokens. If you would list the token distribution after an ICO in a pie graph, a large part of the pie is still owned by the Dev’s or project. Another large part is owned by people who joined a pre-sale. And a reasonable part is owned by people who invested in the ICO. An airdrop adds an extra slice to the pie and that slice will have the most people in it.
An airdrop also plants a seed. When you look at Coinmarketcap you will see a list of thousand coins. Just on page one you can see 100 coins listed. However if you have or had a coin that name is still in your brain. The seed is planted and whenever you check Coinmarketcap and scroll down, the name of the free e-Coin will jump out and people will check how it is doing. If they see an article that the free e-Token is doing well or bad, they are more likely to click it if they own it or previously have owned it. It’s just like advertising!
Looking forward, possible crypto airdrop developments could be projects starting to gift tokens to users who hold tokens in projects that overlap or have some synergy with their own. We could also see projects encouraging other projects to airdrop to their token owners and receiving some benefit in return. Like we already see happening at the Ethereum, Waves, NXT & Komodo platforms.