Because when POS happens, AFAIK the minimum amount for you to become eligible to stake must be 32 ETHs.
32? That's an insane lot just to start earning passively and the returns only start from 4% onwards.
Yes, most of the articles that I've read that's the minimum requirement. But if you are one of those who bought it somewhere around $20-$80 that's a fair price. Still, that's ethereum and the current price makes it quite expensive.
It's a better and cheaper coin I'd guess to have it on stake. Dash requires you around $72k to earn passively through its masternode.