Even the batteries are not interchangeable on phones. You'd think all phones should have the same exact battery, that this kind of standardization is beneficial for phone manufacturers as it helps them bargain with their parts suppliers but no for whatever reason we can't have that.
Edit: I am not saying just user replaceable. I mean standardized so the same cells in a 2024 phone also works on 2025...
The interfaces and the external dimensions can remain the same even as the internals change though, right? And you can have more or fewer cells. The cells don't have to be cylinders, either. They can be flat.
Who will make these custom battery pouches for old phones though? Think my old Poco x3 pro, not the iPhone 17. I am sure there are tons of people willing to make batteries for the iPhone 17 but I feel like the interest wanes as the phone gets older?
For older phones, the batteries we buy are likely also old stock left over if we can find some in stock anyway, right?
Edit: I am not saying just user replaceable. I mean standardized so the same cells in a 2024 phone also works on 2025...