In many role playing game genres, acquiring enough food to live on is often a trivial manner. In a modern setting, you usually just take some of your cash and head out to the local store or fast food joint. If you are playing a science fiction campaign, there's often a shipboard nutrition center that can squirt out some vitamin loaded, synthesized junk for you. If your genre is choice is cyberpunk, you are probably eat less and less these days since you replaced most of your organic body with plastic and steel components. Even in fantasy worlds there are often plenty of solutions for hunger. If you get a craving in your gut and you simply head to the nearest tavern. If that fails then someone else in the party often has a spell or a magic ring to solve your problem.
The post apocalypse settings often do not have such quick and easy options.