No it is not a must. But many college students need money, and during summer they have more time to work. While they are in school, they have classes and other commitments. Unless they want to go to summer school they will have more time to work and therefore get more hours and more money. I do not think college students generally get a job simply to keep them busy. We are very busy during the school year, and spend a lot of our time studying and doing home work. Summer is our time to relax, or do more school work. I do not know any college students who want a job simply to keep them busy.