An average household budget doesn't have a single earner. When you're broke, you have roommates. In more expensive places, until you find a partner to live with you often have roommates.
Our society right now is an outlier. Throughout most of history, people lived much more communally than we do now, and there is good reason to be trying to move back toward that; however, that's a pretty major shift, and it's not going to happen overnight. It's also probably outside of the scope of this discussion.
Sometimes you're forced to live with some truly awful people. It's not always practical to stay with family, e.g. many people moving to the city for work.
This isn't a bad thing.