Stealing your competitors' traffic and customers

@kacper I have this article on my reading list but before getting there - quick question.

How stealing competitors' traffic & customers can be any good? From the point of view of both sides of course. I understand that if I do so I might be winning but what human and leader that makes me? Don't you think that this approach in movie would be a move of the 'Bad Guy'? If I pictured it wrongly, forgive me and let me read the tactic but the word 'stealing' got me into that thinking :)