On one side you can say, the humans need help in not shooting their allies.
Although... If what we're looking at is "tribal" then you really have to wonder how advanced the Skitters were when the Aspheni showed up that them might have been on par with the precolonial African Bushmen (I don't think that's racist language when used in a historical context.).
But you have to wonder if the harnesses are completely responsible for the radio telecommunication, how did they converse pre Aspheni?
I watched Joe Doe a couple weeks back, and just because all the baddies used sign language consistently, it was assumed that all the baddies were deaf. It was a byproduct of their other enhanced abilities, that they lost the ability to hear in exchange for telepathy and telekensis... BUT! It turned out near the end that we discovered that they could all hear very well with perfect ears, it's just they were super paranoid about NSA listening devices recording their conversations.
The Skitters have a lot of hands. Their sign language would be very complex.
It's also possible if many generations have been slaves to the Aspheni, that they may have lost their indigenous language, and wouldn't know how to return to uniform sign language if something did happen to their harnesses.