I'm not sure this would work. Many people that I've noticed seem to hide their networking gear, usually in whatever room the service comes in from the ISP (whic

I'm not sure this would work. Many people that I've noticed seem to hide their networking gear, usually in whatever room the service comes in from the ISP (which is more often than not basements), because that's the most convenient place without running wires all over the place. People are typically using their systems everywhere but those rooms, because WiFi makes it simple to put a system wherever it is most convenient. Even if assuming, say, 40% of users have their main system in the same room as the modem/router, it's unreasonable to expect a lot of those users to use such a feature. Adding the cost, complexity, and size to a system for a feature very few users would use seems almost ridiculous. Although, you could probably argue it already has one - macOS has native capability to share your ethernet connection wirelessly. No idea how many devices this could support, and it obviously lacks any features you would find in a router (firewall, port forwarding, etc.), but it's certainly an option.