No more e-waste as well. And, as the regulation moved from micro USB to USB-C, it's clear that innovation is still possible, within regulations. That's also why you can't have jet-engine powered cars on the streets.

It seems like all that's mandated is that a USB-C charger would be compatible. You can still run a proprietary protocol on top of it if you wanted or use a hybrid, proprietary connector as long as a standard USB-C charger would still work.

What innovations are ruled out by mandatory use of the USB-C connector? It supports more power and data than a mobile device is ever really likely to need.

All that's left is the physical form factor and I'm not sure there's a lot of room for improvement there, especially enough to justify the tons of electronic waste.

It's not restricting to only USB-C. You can go beyond that with new innovations, but you need to maintain compatibly with it.