为什么在使用实例成员 obj.myFunc() 调用时函数没有被挂钩？

class Myclass
{

public:
    virtual void myFunc() = 0;

};
class Derived : public Myclass
{
public:
    void myFunc()
    {
        std::cout << "Actual method is called" << std::endl;
    }
};

    void __fastcall hk_myFunc(void* thisPtr, int edx)
    {
        std::cout << "Hooked method is called" << std::endl;
    }

typedef void(__thiscall *fPtr)();

int main()
{
    Derived* ptr = new Derived();
    ptr->myFunc();// Output : Actual method is called.
    void** vTPtr = *(reinterpret_cast<void ***>(ptr));
    DWORD oldProtection;
    VirtualProtect(vTPtr, 4, PAGE_EXECUTE_READWRITE, &oldProtection);
    *vTPtr = reinterpret_cast<fPtr>(&hk_myFunc);
    VirtualProtect(vTPtr, 4, oldProtection, 0);
    ptr->myFunc(); //Output: Hooked method is called
    Derived obj = *ptr;
    obj.myFunc(); // Output : Actual method is called. Why ??
    return 0;
}