If people are having consistently poor mobile experiences because of poor battery optimisation across websites, that should create market demand for smarter devices/mobile browsers, better development tools and modern standards etc., right?

Well, my point is these problems are created by "converting" what would traditionally have been static content into dynamic. I'm not sure there will ever be a way to make that as efficient as static. Creating a problem and then fixing it doesn't mean you've actually advanced anything. But I suppose you're right in that it'll create demand for devices with longer battery life, if not in a roundabout way. There are probably easier ways to achieve that.

Hands down the most common case I come across is constant DOM changes without any growth cap using something like a circular buffer. Eventually the browser just churns doing constant GC. Travis CI was a big example of this, but the huge set of blog widgets out there are typical culprits as well. I'm not sure how new hardware could possibly address that.