Are non-static class members destroyed even without a destructor?

In Bjarne Stroustrup's "The C++ Programming Language (4th edition)" in section 17.6 (Generating Default Operations) it mentions this:

If the programmer declares a copy operation, a move operation, or a destructor for a class, no copy operation, move operation, or destructor is generated for that class.

Thus, I'm confused why the SubObj destructor is called in this program:

#include <iostream>
using namespace std;

class SubObj {
    public:
        ~SubObj() {
            cout << "SubObj Destructor called" << endl;
        }
};

class Obj {
    private:
        SubObj so;

    public:
        Obj() {};
        Obj(const Obj& o) {};
};

int main() {
    Obj();
    cout << "Program end" << endl;
}

When compiling with g++ I get the following output:

$ ./a.out
SubObj Destructor called
Program end

Based on my understanding, I expected the default destructor for Obj to not be auto-generated because I defined a copy operation for Obj. And thus, I expected that the SubObj member of Obj would not be destroyed because there is no destructor for Obj.

Thus, I'm wondering: are object members automatically destroyed even without a destructor? Or is a destructor somehow being auto-generated for this example?