A thought about engineering students

I have been an engineering professor in the last three years. In these years I have seen great students, good students, and sometimes bad students. I think the main differences between the groups were their inclination towards engineering skills, i.e. mathematical skills, ability to decompose complicated problems into manageable sub-problems, and ability to see the bigger picture. This led me to believe that some students are probably not cut for engineering. This doesn't mean they are not intelligent and I believe that many of them can have great skills in other professions.
So, why, then, are they studying engineering instead of other things they could enjoy and excel in? I think the problem stems from the early age in which American students go to college. At 18 they start, which means that by 17 they already supposed to know what they would want to do in the future. At this age, many young students are still not quite mature enough to make such decisions, and they are probably influenced quite a lot by peer pressure and parents pressure. As a result, their decision depends on factors other than their abilities and wishes, which should be the deciding factors.
What is the problem? The problem is that, in many, cases, these students will start their 4 or 5 years in college studying for engineering, accrue a huge debt in student loans, and then will not be able to enjoy practicing engineering. Many of them may even decide to drop out of college or change their choice. I had a brilliant sophomore student once that dropped from engineering because after two years in college he realized that he wanted to become a nurse. Another good student of mine has been wavering between continuing his engineering studies and becoming a player in a rock band. When he told me about his wish to play with his band in New York his eyes used to sparkle. I couldn't see that sparkle when he talked about engineering: he just didn't enjoy engineering that much.
One measurement for colleges is retention: the ratio of students that complete their course of studies relative to the ones that finished it. I believe this is a very problematic figure of merit: it doesn't take into account the most important thing: that people LOVE what they do. True, engineers make more money than band players (except the really successful ones), and certainly more than nurses. However, payday is only one day a month (or two weeks) whereas joy and job satisfaction is something you live with for every day in your life.