I think the reason EA added this was to expand on the college experience. What I mean by that is some people don't go to college but will take classes for a bit of training in whatever they need to do to help them progress in their careers in real life. Add the classes to the research a sim can do with this. I believe this is to give the player more flexibility in their gameplay. As far as why your sim didn't increase in their skill this I don't understand, it seems that they should have increased in their skill.