The difference is that if they monitor what you do
illegally they can't do anything to you.
But if it becomes legal to do so, they can punish you for whatever it is that they don't like.
It could make the country a better place.
I mean suppose someone had a Kindle
that they knew was stolen. They could track down the sorry --- thru MR and raid his home to arrest him.
Think "Minority Report". Now you've got the idea. It's a wonderful world.