While you can't trade with minor races in the trade window, you can send a freighter to their planet to establish a trade route.
Sending a freighter or a transport are the only two ways to interact with them, so they aren't very useful. It has been mentioned that if you want a race to be less than normal, choose one and set its intelligence to the lowest level in the setup of the game. I haven't tried this. I just don't use minors.