> Phone batteries do not do this - they are designed to fit in a certain (few) phones, and market change on phone sizes mean there is no standard size.

It would be nice if that wasn't the case.

I've seen power tools from certain companies adopt the same battery type across multiple of their tools, so that they are interchangeable. I can imagine something like that happening industry-wide with a bit more lawmaking, like happened with USB types.

Actually, it would be even better if we had a few common phone battery standards and every manufacturer had to use those (ideally with removable batteries). This might mean that phones would have to be built with the batteries in mind, not vice versa, which doesn't seem like a bad thing to me.

Then again, personally I wouldn't even mind if there were like 10-20 common phone form factors in the first place.