why is the destructor call after the std::move necessary?

Question

In The C++ programming language Edition 4 there is an example of a vector implementation, see relevant code at the end of the message.

uninitialized_move()

Answer 1

Moving from an object just means that the moved-from object might donate its guts to live on in another live object shortly before it is [probably] going to die. Note, however, that just because an object donated its guts that the object isn't dead! In fact, it may be revived by another donating object and live on that object's guts.

Also, it is important to understand that move construction or move assignment can actually be copies! In fact, they will be copies if the type being moved happens to be a pre-C++11 type with a copy constructor or a copy assignment. Even if a class has a move constructor or a move assignment it may choose that it can't move its guts to the new object, e.g., because the allocators mismatch.

In any case, a moved from object may still have resources or need to record statistics or whatever. To get rid of the object it needs to be destroyed. Depending on the class's contracts it may even have a defined state after being moved from and could be put to new use without any further ado.