I keep my phones for 3-4 years, and the battery life while degraded isn't really an issue.
And that's with recharging it just about every night even if it's not dead.
I had to make the choice of getting another phone (used in great condition, as I do) or pay half the cost I paid to get the battery replaced but also knowing it would still be heaviy used and more likely to fail in other ways because of use.
If labor cost and decreased relaibility weren't factors, swapping the battery would have been the choice.
Now the question is: are there more people like me or more people who need a sealed, hard to repair phone? I don't know but if I did I'd accept keeping the current situation.
While manufacturers do have an incentive to get people to buy new phones, many of them with first party insurance do have an incentive not to pay out as many claims.