You are missing the point of PoS. The point of PoS is not to be better at achieving decentralized consensus than Proof Of Waste. The point of PoS is to achieve sufficiently decentralized consensus without wasting a ton of electricity, therefore harming the environment, and/or wasting a ton of processing power that could be used to benefit society in one way or another. If you insist on PoW, then make the PoW beneficial to society like Primecoin or curing cancer... otherwise it is a waste of energy and processing power.

Furthermore, it is unclear whether Proof Of Waste will work once the block reward halvings stop and no more currency will be printed. Currently PoW coins are diluting their shareholders to pay for miners to secure their block chains. The only coin that is far enough along in its emission curve (Dogecoin) needed to switch to a merge mine coin because no one was mining it. If it is not profitable to secure the block chain then no one will and it leaves the coin wide open for attacks. If the biggest PoW coin's values don't rise enough so that the transaction fees alone will pay for miners to secure the block chains, then they will need to eventually change their consensus algorithms or be left wide open to attacks. In other words, it may be inevitable that all coins eventually have to switch from Proof Of Waste, so that is another reason why it is important that PoS exists and people are altering and improving upon it.