Custom allocator not been used

Consider the following code:

#include <map>
#include <iostream>
#include <string>

class MyAlloc : public std::allocator<std::pair<const int, std::string>>
{
public:
    MyAlloc()
    {
        std::cout << "my alloc ctor" << std::endl;
    }
};

int main()
{
    std::map<int, std::string, std::less<int>, MyAlloc> ms;
    ms.insert(std::make_pair(2, "hi"));
    std::cout << ms[1] << std::endl;
    return 0;
}

I've created my allocator to fit the default one. But I see my allocator not been used, not even constructed.

when I'm using a debugger I can see the map is using the default std::allocator.

Is there any problem with my allocator?