Not many years ago, BTC was worth couple of $. You know why?
Because it was literally for free, any kid could run a CPU miner for couple of hours to earn couple of BTC.

If you would be giving away gold bars, gold price would plummet.
Same applies to airdrops - getting something for free.

But the difference between gold and airdrops is that gold had value for thousands of years while airdropped never had any prior to airdrop.

And advertising something to have "million $" value before first 1$ worth of coins/tokens did change hands is really a joke.