But it does help. It gives people qualifications in most cases that they can use in civilian life. I spent two years studying in the R.A.F. and the qualifications I gained got me jobs once I left. So personally I see the benefit of national service. If you've never served then you don't know.
Bully for you, I spent that time drinking and dropping out of Uni, I feel that period helped me. If you've never been a University layabout alcoholic, you don't know.
Unlike others I wouldn't suggest my experience should be forced on all, why do you?