c++ - What is the point of deleted destructor?

I come across the rule (section N3797::12.8/11 [class.copy])

An implicitly-declared copy/move constructor is an inline public
member of its class. A defaulted copy/ move constructor for a class X
is defined as deleted (8.4.3) if X has:

[...]

— any direct or virtual base class or non-static data member of a type
with a destructor that is deleted or inaccessible from the defaulted
constructor, or

[...]

But I can't get the point of deleted destructor appearing in a virtual or direct base class at all. Consider the following simple example:

struct A

{
    ~A() = delete;
    A(){ }
};

struct B : A
{
    B(){ }; //error: use of deleted function 'A::~A()'
};


B b; 

int main() { }

DEMO

It's perfectly unclear to me. I defined 0-argument constructor explcitly and it doesn't use base class destructor. But compiler thinks otherwise. It won't work even if we define B's destructor explicitly:

struct A

{
    ~A() = delete;
    A(){ }
};

struct B : A
{
    B(){ };
    ~B(){ };
};


//B b;

int main() {
}

DEMO

Couldn't you clarify that thing?