What is the purpose of returning a value by reference?

Question

C++ / C#

I used to think that returning a value by reference differs from returning a value by a pointer in that in the first case it would not be necessary to dereference the pointer, but apparently this is not so. I wrote this example:

#include <iostream>

int& func(int &a)
{
    std::cout << &a << "\n\n";
    return a;
}

int main()
{
    int a;
    int b;
    b = func(a);
    std::cout << &b << "\n\n";
    std::cout << &a << "\n\n";
    return 0;
}

I thought that three identical addresses would be displayed, but this is not so. If you return by value, the result will be identical. What is the purpose of returning a value by reference?
If we return a pointer to a variable, then in the caller it has the same address (we returned it) and information at this address, but the pointer address will already be different. If we return a variable by reference, then the address of this variable in the caller is already different, only the information remains the same. Why and why?

Answer 1

b = func(a);
This is where you took the reference returned by func and copied the value into b. So the &b below will give you the address of the variable b, not what you wanted.
Returning references is convenient when you need to return a value without copying and it always exists. Because a function that returns a pointer can, in general, return nullptr as well. On mind, it would be necessary to check this pointer before dereferencing. But links - they always point somewhere.