But we are, for ~6 years now? If you have a Samsung Galaxy phone - the most sold phone models in the world (trades place with Apple sometimes) with 60m+ devices/year sold, just plug it in and there you have it. Full peripherial support, you have a perfect multitasking desktop environment and access the same files - called DeX mode.

And yet, this question is here - somehow no one really uses it or even knows about it.