In severe cases, there may also be tupperware containers that everyone is scared to open, full of unidentified stuff that may once have been food, or dairy products that have passed their expiry dates multiple times. In these cases, it is not recommended to attempt to clean the fridge without proper biohazard gear.
Bachelor fridge is usually more of a cyclical phenomenon than a permanent state. People who suffer from bachelor fridge often go through phases where they buy real groceries and cook meals, alternating with periods of bachelor fridge.
Roommate 2: I was thinking we should clean the fridge, throw out all the rotten stuff, and then go buy groceries and cook ourselves a nice dinner.
Roommate 1: Nah, I'm too tired. Let's just order pizza.