Well, what is stopping people for creating switches that go into the distribution panel? They can even fit as circuit breakers, so no change at all is necessary.

One would need a large diversity of products to make it work, what puts it out of reach of any small manufacturer. But why the large home automation sellers insist on their "you must add this huge panel, pass all those wires around, and can't retrofit any new device once the layout is settled" technologies is a mystery to me.