What is the purpose of switching to PoS(question by a noob)

If ETH 2.0 doesn't bring the fees down, what is the sole purpose of switching to PoS, PoW would be more decentralised(compared to PoS). PoS is just to give more of the voting rights to the devs who hold loads of pm Ethereum? Eth has roll ups but ETH did not start for/with roll ups. I may be wrong, and am ready to learn if proved wrong. Thnx