The Minutemen, good in concept but easily corruptable. Without the Sole Survivor, they would most likely become what they had become before and once again destroy themselves. Not to mention, they are the most boring faction whom give you repetitive quests, and they even have the most boring characters.
The Railroad, once again decent in concept (if you believe synths are equal to humans... which I dont neccesarily agree with) but once you complete their questline, their reason for being in the world is gone. They will break apart as their goal will have been completed.
So for those of you who have done these playthroughs.. what was your incentive because I definitely need one.