Yes! And I blame OOP. People are taught that everything should be a magical black box, designed so well that after implementing it - you never need to change i

Yes! And I blame OOP. People are taught that everything should be a magical black box, designed so well that after implementing it - you never need to change it, only add to it along the predefined extension points. So if that's true - even modifying the base classes in your own system feels "wrong", never mind the "other people's code".