Why do batteries need to be unique for each model? Some laptop lines (e.g. Lenovo) share removable batteries among models with similar power needs. Same used to be true of phones which had removable batteries from the same phone vendor.
That was before flagship phones needed to become thinner and bigger every few months. Can't have commonality of parts if your six months old battery is thicker than the whole new phone.
(There's still plenty of phones with replaceable, more-or-less standardized batteries available… but it's $50-200 phones that nobody wants to buy because they're not sexy enough. Even though they've been fast enough for years…)
Because everybody wants to be special. Size, weight, optimalization, screen edge corner angle, etc. It is a senseless, unsustainable development practice that creates much waste each year. Nobody seems to look at the future, everybody just wants to win in the here and now.
4 degrees later, we are all gone. The batteries remain, for a while. In 2135 CE, the last Samsung battery too will catch fire, starting an unstoppable wildfire that will consume much of Eurasia, along with whoever survived the previous social collapse. Then, only ashes will remain.