The roommate relationship is highly friable
The relationship between roommates is one that is highly friable - it crumbles easily. This is more true for roommates than it is for other types of relationships (e.g. friends, romantic partners, coworkers). Even close friends who are roommates can have a strange layer of tension imposed upon what may have been a stable preexisting friendship. There are so many little ways to introduce conflict, annoyance, or neglect into a relationship where you are primarily bound together by the fact that you share a home, and in other types of relationships those possibilities either don’t exist or are mitigated by a deep emotional bond that incentivizes overlooking such transgressions.