Possibly. It's also been said by some that they put a membership cap on the families so one family couldn't grow too large and pose a threat to the other families. And then there is also the issue of law enforcement scrutiny. I think that they simply decided that there was enough manpower for the families to function properly. At their height the Five Families were estimated to have about 1500 made members and thousands of associates. They were pretty much in control of New York at the time.