Most people eventually outgrow the idea of living with a roommate. A desire to have personal space in your living conditions only increases when traveling.
After a long day of exploring the city, you likely want to crash in a hotel room, away from strangers. But, for those that want to try spending the trip near a bunch of strangers in a shared area, a hostel can be a fun option.
In the long run, choosing a hostel for lodging can save you a great deal of money, leaving you with more cash to spend on other activities. But, sometimes the risks of a shared sleeping space can even outweigh extra money in your pocket.