That’s HDMI.

...which can't carry power or a network connection - both things that could easily be provided to the module through a single slot connector.

Why would it need to carry a network connection (apart from CEC), when the point is that the display itself shouldn't be connecting to the network? Standardize on a certain barrel connector a certain distance away from the HDMI port, with the ethernet/wifi on the other side of the module.

It'd be great if say Google pushed TVs in this direction ("Google Display with smart cube. Never have an outdated TV again" or something), but I bet the decommodified dumpster fire of baked in software benefits them too much. After all, the last thing any of those companies in the business of selling "content" wants people to do is to end up plugging in a Kodi box. It's like banks with overdraft fees - by abusing your customers, you make them worry that switching will result in even more abuse, thus encouraging them stick with the abuse they already know.

HDMI can certainly carry Ethernet

Yes, I know, also power, just not a usable amount. Ethernet over HDMI is rarely implemented and caps out at 100Mbps. Even if you have it, that still leaves you with a power cable and big ugly box to put somewhere.

The bit rate of all the current streaming providers and Bluray players fits well within 100Mbps, so I'm not sure that's really a limitation?