That is all very well and I really appreciate Apple's long support for iPhones, but Apple did popularize firmly bonded batteries in its phones and even in notebooks. A battery is a wear part and should be easy to replace. Every thing else leads to more waste.
I do not necessarily disagree about the fact that batteries should be easily replaceable. On the other hand, I do not think that Apple's motivation was pure greed: if you make the battery an easily replaceable part you also need to encase it in a shell, and make it robust enough that even untrained users can safely handle these. This means that you have to make it bigger (externally) sacrificing actual internal volum…
The battery cells are designed to be fairly robust - punctured a Kindle battery during a screen repair (friends roommate came home drunk, bumped into the table while I was picking away at the glue) and there was a very brief tiny poof of smoke and nothing else. If the battery hadn't been glued, that situation would have been impossible.
I also don't recall seeing any news articles back in the days of near universal user swappable batteries about widespread incidences of users being injured by swapping phone batteries.
It's also less likely you will damage a battery if you just have to undo a couple screws instead of sitting there with a heat gun, from a repair tech perspective - but I've only seen batteries held down by screws in unibody laptops.