Custom allocator method is not called

I am trying to learn and write a self custom allocator - I was expecting that the cout statement should be printed but it never does - what is the wrong am I doing - how to write custom allocator:

#include <iostream>
#include <vector>

template < class T >
class MyAllocator : public std::allocator<T> {
public:
    T* allocate(size_t size)
    {
        std::cout << "Allocation request size " << size << std::endl;
        return new T[size];
    }

};

int main()
{
    std::vector <int, MyAllocator<int>> x;
    x.push_back(10);
    x.push_back(10);
    x.push_back(10);

    for (auto& var : x)
        std::cout << "Value " << var << std::endl;

}

Output

Value 10
Value 10
Value 10