I keep them around, but I usually play a "good" race. I like it when they are in my influence and I can both tax them and trade with them. Plus they respond to me "requests" for tech very favorably since I defend them from any other race rolling over them. For example in my current game I have been asked for help from the Paulus 3 times against the Aceans and have helped them each time, always taking a border planet or two for myself before declaring peace. So the Paulus give me almost anything I ask for, and I give them tech in exchange for influence (going for influence victory).
If I was an evil race (like the Yor) I would grind the to the ground as soon as I got Troop transports

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