That's an interesting point (re: doing something specific) which applies not just to college students. The truth is once you have clarity and vision, what ever it is you are doing seems like poor usage of your time. Having said, it's not easy arrive at that kind of clarity or vision.
One can argue that there is no clarity of vision involved. Rather, for every individual like Gates who gets lucky with a good business opportunity, there may be many equally qualified individuals who do not get a lucky break with a good idea.
It is always assumed that success and failure in business corresponds directly to skill. I doubt this assumption and suspect luck has a lot to do with it. Once you get your first success earning you several million, many doors open to you.