I'm going to say that typical resistance machines should not form the bulk of one's training - get your heavy(ish) barbell compound movements done - but I'm behind the OP in the spirit of this thread. There are several reasons I think people should be interested in strength training and should put get some decent heavy physical work done:
-It's fun, honestly it's incredibly satisfying to do and progress at
-Train smartly and avoid injury and you'll decrease your risk of attaining injuries in general by virtue of strengthening not only your musculature, but your bones and connective tissue as well
-It doesn't just make you stronger, there is far more "carry-over" from strength training to endurance than there is from endurance training to strength (not that you should perform no cardio, but that lifting weights does not produce one-dimensional results as many think it does)
-It makes you look better, a small point but worth noting nonetheless
-Obviously, it makes you stronger which is worthwhile in and of itself