What is you benefit as a consumer to have each appliance have it's own unique cable, generally providing same functionality?
For example say I have a small < 100W device that needs to be powered and send data and I'd like to use the same connector for it. But wait, I'm going to put this gadget in an environment where people might knock the cable out so I'm going to use a different connector with a latching mechanism to prevent the cable from coming loose.
Oh no, I can't do that because the government says I can't.
Like OP said if it bothers you don't buy it. That's the market working for you. Diversity is good for the market and connectors aren't one size fits all, no regulation will change that.
Lockable USB C connectors exist. Why do you think these would be banned?
https://uk.farnell.com/neutrik/nmc-c-hr/usb-c-chassis-with-r...
fwiw the latch on those things is pretty terrible. What if I needed something like a Speak-On connector which twists? Can't do that with USB-C.
So now it's USB-C, and... that's it? Forever? No point in innovation in the cable space, because nobody will be allowed to use anything else.
And "all small appliances < 100w?" So either I'm paying for a cable capable of carrying data at high speed to power a lamp, or I have separate cables for lamps and phones, but using the same connector, and how do I tell the difference?
Hard pass.
Ideally you won't need to in most cases. That being said, USB used colors to match cables to sockets, with black being the old cable and blue being the newer, faster interface. You could use the old cable on new devices, but you're stuck with slower transfer.
For something like a lamp, it likely wouldn't matter what cable you use, so just use whatever is laying around. If it's for something high speed, just keep the cable separate.
Being able to use a device with a backup cable at degraded performance is better than not being able to use a device. I had a lamp that used a bespoke cable and connector, and when we lost one part, we threw the lamp away. We later found the part, but nothing else used the connector, so we threw that away as well. If it used a USB-C cable, I could just use one of the several I have laying around.