Can't is a strong word. You could 100% put it in the compiler. Yet you don't (for the reasonable reasons you give). The line between compiler static analysis and non-compiler static analysis is a design decision. "defeating the point" is a subjective and pragmatic decision, not one rooted in safety absolutism.
I didn't really phrase this particularly well: I meant that you cannot determine this stuff at compile time because it is inherently a runtime analysis. Of course the compiler could emit the Miri interpreter into a binary if people chose to put the pieces togehter that way.
