That's not necessarily true. A lot of these services are successful because they can charge less and still profit because they don't have the overhead of a full time business. Renting a room or two in your house carries no downside potential. If the rooms stay empty all month, it's no different from before you signed up on AirBNB. In contrast, a hotel has substantial salary costs to cover each month. If they stay empty a whole month, they're in debt and have to make that up next month somehow.