Plumbers/electricians don't require hours and hours of technical reading to be trained in their field. Learning how a toilet works or how to wire a TV isn't as complex as learning the ins and outs of how the human body works
Biology would not train someone in Sports Science, and a lot of the Biology would not be relevant to them in future. Sports Science degrees tend to be a mixture of biology, medicine and of course, sports.
I don't really see how doing Law benefits society more than doing Sports Science, or is any less vocational...
And at the end of the day, if he wants to get into Sports Science, then a Sports Science degree is obviously more useful to him than anything else.
What about Philosophy, History, Geography etc do you think it is that gives someone a "worthwhile body of knowledge", and why is it important for someone to become worldly? Personally, I think someone going to University to become w*s* and have a wide range of knowledge is, in a way, wasting their time more than someone doing a more focused subject - unless they plan on making a career of going on TV quiz shows.