The only reason I use a case is that the iPhone is close to unusable on a flat surface without it.
I'm arguing that the sealed / glued / tightly packed / irreplaceable battery thing helps keep phones working for longer.
Of course the counterpoint is that often the battery is the first component to go, and this law is intended to make it easier to keep them in working order for longer.
Nokia actually did an Android phone just before MS acquired them which they then promptly killed. And then of course they pulled the plug on the whole business unit. HMD apparently still makes feature phones based on Series 30. That's the pre-smart phone platform that a lot of Nokia fans remember fondly. The famously indestructible phones.
They're somewhat of a standard in DIY circles because they're a familiar form and all of the support stuff for them has existed for decades.
Even if you stripped a 5G phone down to a Series 40-esque interface the 5G radios alone would use more power than a whole 3310.
In order to get the power density modern phones need they require high power Li-poly batteries. An extra 3mm worth of ABS shell is a lot of lost capacity. You can't sell user serviceable Li-poly batteries without a protective shell. You'd never get a UL rating because Li-polys are dangerous if mishandled.
I came across them in portable radios (portable FM radios, small global radios, plane listening radios and similar).
Also interesting to know is that BYD was supplying a lot of phone batteries back then. I think they also supplied to Nokia. Phone batteries is what made them big.