Not everyone is motivated purely by money.
Also if you ask people, the majority dont know what they want to do when they finish their degree. I dont think anyone sets out with a definite plan (unless its something obvious like becoming a nurse/doctor, but even then you can specialise and you might end up doing something different from what you originally intended). Also if everyone did courses which did lead to employment specifically related to that degree and no one did courses because theyre interested and enjoy it, a lot of subjects would disappear altogether and we'd have a lot of people doing courses they arent interested in but it will lead to a certain job, meaning less motivated people performing badly. If people are talented and able and put the effort in then they can and should do whatever they're passionate about, regardless of what the final outcome will be. Having a degree in something shows a lot about you as a person and makes your employment prospects broader than people who havent got one (not that Im saying you *need* a degree to get a good job, but it obviously helps and gives you an advantage and shows you have certain skills).