> imagine a world where ...

It already works like that.

> customers never bother to submit their own T&C's so they're not fairly represented

You can't. Not a question of bother.

> if you don't, then don't use the service

The problem is that this is mostly not an option. The service doesn't have competition or competitors don't have better T&C. Sometimes, like in the original commenter's example, there is a legally enforced monopoly.

At least the government has to enforce certain rights when using government provided services.