[int_19h]

What I don't get is why phones can't be configured to just never charge past 80% or so, for people who rarely need that 100%, and would rather the battery wear less.

It's a thing for some laptops; e.g. Lenovo specifically advertises such a setting.

[fulafel]

Apparently you can do it on rooted Android, though I haven't tried it (eg https://www.androidexplained.com/battery-charge-limit/)