Can you keep a sandwich in your backpack for weeks and it won't go bad?
Can you eat a sandwich without any crumbs?
Can you eat a sandwich in meeting rooms with "Drinks allowed but no food allowed?"
There are many more use cases than you have thought of
"It would be clear that if we wanted to avoid such monitoring that we would have to do something special." Pretty sure the government would want to make that as opaque as possible
A goal of x86 was backwards compatibility, but it has never been perfect, i.e. when software was written that relied on undefined behavior that later chips implement differently, etc.