Because there are millions of idiot suckers who buy and mine pre-mined scam coins and just dump money to these shitcoin-producting scammer devs.
There is a sucker born every minute, and a lot of devs are taking advantage of it because those suckers don't know a fair launch when they see one.
The devs premine a bunch and then dump it once it gets on an exchange.
The ANN thread is just full of complete shit.