"In reality you'd use the fact that USB-C can fulfill a bunch of functions simultaneously, so your display can charge your laptop and provide USB A ports for your legacy mouse and keyboard."
Well, USB-C mouses, keyboards, flash drives and displays (especially, charging displays) are still exotic. And they are very expensive. You also forgot that there are also other ports such as HDMI, Ethernet and VGA which were also abandoned in favor of a slimmer chassis. Just look at how common USB-C to VGA adapters are. Using docks on a daily basis is fine but the original point was that, maybe, it is not worth it. Do not get me wrong: USB-C + USB 3.1 + Thunderbolt 3 is a very nice piece of technology. We are going to see more and more of it in laptops with it but I doubt that it will replace USB-A ports anywhere except laptop sector.