It is a wasting because it could be done with staking, that way the could shouldn't need miners. And i think this is why ETH is moving to PoS.
And it's a waste if the energy cost is bigger than the mined coins...
You have a valid point but I always feel that PoS makes richer people more richer and poor gets poorer. The rich can always buy more coins and stake to get more coins and it's similar to gaining interest in money in bank. While in PoW there are a lot of things involved and you can't just mine more because you are rich.
Bitcoin could be mined with a simple GPU in starting and you don't have to buy anything to grab some bitcoins while to grab PoS coins you must buy those coins first and then you can earn interest on that. Plus, PoS gives much more power to someone if they can grab a big amount of coins from the market and loosing the actually meaning of decentralization.