The demand simply isn't there for replaceable batteries. I know there's a loud minority on HN and other tech focused sites, but it's simply not something most people care about. How well did extra batteries sell when they were common?
Considering how phones have pleateaued, I bet you'd get a lot more buy in if you frame it like that.
This is about avoiding electronic waste, not being able to plop out a battery every day. People may not care about that, but some people don't care about pollution in general.
But the EU thinks society will benefit from less electronic waste and more durable devices. Or at least EUropean society, which AFAIK leans towards importing smartphones rather than making or design them. And this is far from the first time governments enforce features on products that the market doesn't seem to be demanding.
But is the EU thinking of something about enforcing longer software updates timelines? I suspect this law won't be so effective without it.
But then it doesn't exist, right? Like today, which phones do have replaceable batteries? So the free market doesn't work and the government needs to step in. Blame the manufacturers (or the customers if you want).