Vagrant vs. VirtualBox ? - A false contradiction

"Why should I use Vagrant instead of just VirtualBox?" - There are quite a lot of questions and answers of that type  in the net. The questioners seem to belong to the group of operations engineers, e.g. application supporters, database administrators, etc. The answerers seem to belong to the group of developers. Hence my first clue on this queer debate is, that it may be a question of conflicting priorities in the field of the Devops movement.