I didn't for a minute suggest it couldn't. Rather, that a single wire doing all that plus power is going to be a spaghetti like mess, and a dock might be the better solution. I don't see anyone crying out for a single cable that has two adapters going off to monitors, another to the keyboard, another to the mouse, another to network, another to an external drive and then a few spare for regular USB use like SD cards, charging your phone, etc. Presumably, the solution is a usb-c hub, which begs the question why that's better than a dock which provides all the same at your desk, plus the laptop having sufficient ports for when your away from the mega cable?
Also, from my understanding, usb-c does have some practical bandwidth limitations that could be an issue if your driving a multi-head setup and want decent bandwidth remaining for external disk and Ethernet. Admittedly that's going to be less common.