Yeah, actually they did that too. Ethereum had a "premine" of 12 million ETH that went to the developers.
Back then, It wasn't worth much. That's 36 billion dollars worth of crypto now.
Nowadays, if someone launched a new crypto with that much premined, it would be considered a scam.
-Its actually a sort of smart way to incentivize coin development.
You start off with a ton of worthless coin, more than you'd ever reasonably mine, but it drives you to keep developing your coin and keeping it stable and growing without boom/bust cycles.
If you tried to sell it early, it might collapse the coin or delegitimize your coin.
Not saying this was the thought process and it would be nice if it was better regulated, but it's actually a really sharp way to reward the creators of a coin while also helping build trust in the stability of an alternate currency.