If you believe in free market capitalism, people should migrate from PoW to PoS coins, because PoS coins provide the same features with less expenses.
In practice this won't happen, because PoS coins don't deliver the same features (security, decentralization, permissionless) or the market doesn't believe they do.
Also the savings with PoS are not passed to the users of the cryptocurrency, but to the stakers, or big holders of the cryptocurrency. How do we even know, that these people will spend the money they make using some more enviromentally friendly way? Maybe they just buy lambos with the money and fly around with private jets.
Mining is quite small amount of the total transacted amount of BTC daily, and people are willing to pay the cost. If you want to replace Bitcoin with some more enviromentally friendly thing, you have to offer the same capabilities (or better). PoS coins fail to deliver this.