std::move does not move

gistfile1.cpp

#include <iostream>
#include <vector>
#include <string>
int main() {
  std::string str1 = "AA";
  std::vector< std::string > v;
  v.push_back(str1);
  std::cout << str1 << "\n"; // AA
  v.push_back(std::move(str1));
  std::cout << str1 << "\n"; // AA
  std::cout << v[0] << "\t"; // AA

  std::string str2 = "BB";
  std::cout << str2 << std::endl; // BB
  v[0] = std::move(str2);
  std::cout << str2 << "\n";  // AA
}