The energy is being spent on securing one of the most secure networks in the world, so it's not necessarily being wasted. I think we can all agree that we should always be pushing for improvements, but who's to say that proof of stake is an actual improvement? It certainly has its merits, but also comes with just as many, if not more problems. Switching problems with other problems isn't a solution.

I do agree that we should look into replacing proof of work, but only when we have something that is clearly better. In the meantime, if it's not broken, then don't fix it; proof of work is in place to protect the network, and it has done that perfectly well thus far.