I just studied this in my US History class, but here is a very vague reason. When Ford had the idea of an assembly line, it would mean that instead of having to train his employees about how to make a whole car, he would use a very different method. By hiring many people and training them to only be skilled in a certain section of a car ex: seat, tire, etc. he would be able to make cars quicker, resulting in more products being sold. At this rate, he would also make more money because he can produce an automobile faster, thus making much profit for his company.