Why do I need a default contructor o Point class in this case?

I have this simple example of using a functor in C++:

#include <memory>
#include <ostream>
#include <iostream>

template <typename T>
struct Point {
    T x, y;

    Point(T x, T y) : x(x), y(y){};
    Point(){};

    Point<T> operator+(const Point<T>& other) {
        this->x += other.x;
        this->y += other.y;
        return *this;
    }
};

template <typename T>
struct AddSome {
    AddSome(){};
    AddSome(T* what) { add_what = (T)*what; };
    AddSome(T what) : add_what(what){};
    T operator()(T to_what) {
        if (ptr) {
            return to_what + add_what;
        }
        return to_what + add_what;
    };

   private:
    std::shared_ptr<T> ptr;
    T add_what;
};

int main(int argc, char* argv[]) {
    Point<int>* pt = new Point<int>(5, 6);

    AddSome<Point<int>> adder5(pt);
    Point<int> test = adder5(*pt);

    std::cout << test.x << " " << test.y << std::endl;

    return 0;
}

In the version above it works very well but it doesn't work at all if I delete the default constructor of the Point class.

What does the compiler need this constructor for?

via Chebli Mohamed