If an STL container lacks a method, it's a hint that 'here be dragons'. For example, random access of a std::list: it's possible, but you don't want the uninformed to be doing it without considering the consequences simply because it's easy to write.
What do you do about the memory allocated for the first element? That's a decision for the programmer to think about, not for the standard to enforce. A std::deque may deallocate.
Additionally, you can just do:
std::stack<T, std::vector<T>>