When I've pictured my "ideal" phone in the past, I've regularly had long battery life as one of the key features. But I've thought about battery life as something that hasn't improved. Because most people have probably been charging their phone every night for quite some time.
However, you could probably argue that battery life has always been increasing. The problem is, so have our demands.
Sure, more powerful chips require more energy to run. So an iPhone 15 will naturally require more resources than an iPhone 5. At the same time, we also weren't expecting an iPhone 15 to record 4K HDR video without affecting the battery life.
It's probably not a big revelation to many. But it's a perspective that might be worth considering when judging the evolution of technology.