Why do they jump to it? Tribalism and xenophobia, the latter is one of the few socially acceptable ways of expressing it against "acceptable" targets. It doesn't matter that Bob's Books does a shit job he is one of us. Outside businessmen are The Other. I mean the last time that sort of thing was judged negatively was response to Post US Civil War lynching of "carpetbaggers". Hell the modern use of it for opportunistic moves of politicians is still the same xenophobic arbitrarily designated wrongness.

It seems obvious but nobody ever calls that behavior what it is, along with "cultural protection" which is really an attempt to treat the choices of others like your own property in what would be called overwhelming arrogance in most other contexts.