Tying Bitcoin’s security to real world energy expenditure is what makes it robust and decentralized. PoS is an inherently insecure and fragile system. Governments can co-opt or shut down PoS chains quite easily. Not to mention they run on perverse incentives where the largest holders get to determine what transactions are valid and reward themselves with more coins. PoS or likely works well for scaling layers but base layer needs to be preserved as PoW.