Not because GPS tracking system is a kind of fashion, or it gives you a wonderful user experience, or it brings you a joy which electronic game can offer like angry birds. It is because of the fear of uncertainty, security from human beings' minds. People want to control their life, manage it, improve it.
People usually say bosses should not bother the details. They should focus on more important things like business relations with big clients, company future, market trends, whole goals. But if it won't take them much time, they may want to see the outcome of these businesses. as the bosses of fleet companies, they also would like to know where are these vehicles.