One of my roommate horror stories was when my roommate never cleaned up after himself. The kitchen was always a mess with dirty dishes piled high and food crumbs everywhere. It attracted bugs and smelled really bad. I had to constantly remind him to clean, but he just ignored me.
The inconsiderate roommate is also a horror story. They don't respect your study or sleep time. They might have loud phone conversations or play video games with the volume up when you're trying to study or sleep. This can lead to a lot of stress and conflict in the living situation.
Maybe it's because the market demand for it is relatively small, or there might be certain social or cultural barriers preventing its widespread production.