Yes, the body is still in full gear burning calories for a time (up to an hour) after exercise (especially cardio). After that your metabolism will slow again. So the idea is to burn as much fat from your body for fuel as possible, rather than fueling it with food, especially carbohydrate-rich foods which are converted faster to energy and will prevent the body from burning it's own fat stores first. However, if you aren't worried about burning fat, there's really no other reason to wait.
On the other hand, on days you do strength training or muscle building workouts, eating a short time after your workout is fine, as your metabolism isn't in high gear the same way, and the extra protein that you might consume will help to begin rebuilding your muscles.
This is not to say that you should overeat. If you take in more calories than you burn during your exercise, you will gain weight.