Bedrockgames
I post in the voice of Christopher Walken
One part of the problem here is that historically 'primitive tribal societies' have been so vilified and derided that there is sort of vicious association circle here. Most of the language we have to describe non-city-based low-tech civilisations comes across as at least somewhat offensive. Which is just messed up as such cultures have existed, still exist and are perfectly fine and valid. Granted, in many instance D&D doesn't even try.
I think we are getting very far afield of the topic. But I think it is a lot more complicated than this. Also, I think there are different perspectives on this expressed in a lot of fantasy. That is one of the reasons it is interesting Conan is so foundational. That is very much written as a critique of city based society. A lot of how this plays out is going to depend on what historical perspective you are looking through when you draw inspiration. You see this in movies all the time. If you are watching a movie about Romans, with more of a Roman point of view, the Germans are going to be more 'barbaric'. If you are watching a movie from the point of view of the tribes in Brittania, then the Romans might look more like cruel occupiers. Most fantasy settings have cities that fit into both types, and have non-city people who fit into both types. And evil is always more interesting, and more gameable, so you are often going to see more of the evil type than the good. Just look at cities that are good for adventuring. If everything is perfect and peaceful, there is less opportunity for adventure. Places with corruption, secret societies, criminal underworlds, etc (all the negative stereotypes of cities) are more gameable. Same thing with tribes of orcs. You can have peaceful orcs and do a deep dive into the complexities of their society if you want (and I have done that, it is fine and can serve a useful function in a campaign), but I think for what most people are looking for, in terms of gameabilty, evil orc tribes serve a functional utility for adventure and excitement.