Lots of people prefer eating smaller servings more frequently, some people need a snack to get through the day. Yet others have varying schedules that cause may fall between meals in a way that makes them hungry.
Regular small meals have been frequently recommended for a variety of diet reasons and is in no way tied to diabetes or other health issues, and is often times better then a glut of food in a single meal. In addition, people prone to hypoglycemia can benefit from gentle gnoshing through the day.
EDIT: Think about marathon runners: they drink water and electrolytes. I'm pretty sure I can handle a workday fully concentrated without eating every three hours.