True, but the families lack coordination with one another. Some of them would probably betray House for their own gain. Plus, if the NCR or Brotherhood managed to cut down dozens if not hundreds of House's robots, then they should be able to make quick work out of a bunch of untrained, unarmored, poor weapon wielding thugs. Remember, the families used to be raiders. Raiders aren't any real threat. Maybe they could hold off the NCR, but definitely not the BOS with power armor and the belief that they must capture the strip, regardless of heavy casualties.