I agree they're good to put into the language semantics, but as a side point on C++11, couldn't the compiler actually assume a bunch of things about those templates, since their behavior is specified? GCC, at least, assumes many things about even C stdlib functions, because it "knows" what they do, so rather than treating them as just regular functions, it can make stronger assumptions about them when optimizing, and/or generate code to implement their functionality internally, rather than linking the library implementation.
You can, but the difficulty, I think, is that this clean separation of pointer types exists along with naked pointers, including void*. That is, C++11 still carries the legacy of C's free-for-all, so the kinds of guarantees that one could get from a C++ compiler - even with baked in knowledge of unique_ptr, shared_ptr and weak_ptr - are going to be limited.
