We've had smartphones without superuser rights for checks notes literally forever. There hasn't been a single mass market phone ever created that required you to run anything as root. Yeah, we can jailbreak phones, but until the law busts up the "app store" model, phones don't need root. General computing devices might, and you might want to turn your phone into one of those, but as the device it's sold as, no phone has ever needed you to have access to, or use. , root privileges.

Because they're not designed to be computers (yet). Operating systems for desktop have given you the power to superuser-up since day one, to this day, and the odds of that changing any time soon is pretty much zero, because without superuser privileges we can't use those computers for what they're intended to be used for.

So yeah, personal gripes: they are wildly and completely different types of devices, for different markets.