OK. 50 or 60 percent of U.S. high school graduates in 2009 went directly to college. What percentage of those do you think are studying academic subjects because they feel the subjects are "enriching their life"? 20%? 10%? 5%? 2%?
The American 18-year-old is not a demographic in which you find many philosophers.
I'm not sure how you can tell. It's easy to form opinions like this about undergraduates that you're teaching, but in practice they're based on virtually nothing. You don't know these people, you just interact with them in a very restricted way for a few hours a week. (And you spend hardly any time at all with them on a one-to-one basis.) At least, that's how I fell when I'm teaching.
I don't think first-years are a fair assessment of any institution. Many of the original 90% partiers will either a) shape up, b) drop out of college or c) some other choice. Good luck -- my friend is also a grad student teaching first-year calculus for "business, social sciences and humanities" .. ie kids that aren't interested in math. In his words, "it's painful".
The American 18-year-old is not a demographic in which you find many philosophers.