You're comparing someone single to someone in a relationship. Two people need "process" to get along, whereas a person on their own does not. An analogy fittin

You're comparing someone single to someone in a relationship. Two people need "process" to get along, whereas a person on their own does not. An analogy fitting to OP's point is comparing two people from Hollywood and Ethiopia living in the same apartment versus one of the cohabiting couples you're talking about. In one case, you'll need expressed rules for each to abide by since they're culturally quite different. Comparatively the other case will have very few rules, because of the cultural similarity. The cohabiting couple will more naturally work towards similar goals without painstakingly negotiating them and laying them out.