Because they're broadened their experience and knowledge with new languages and learning new things. My point isn't so much about learning the very latest thing so much as it is about learning in general. At the very least the people who spent the last 4-5 years learning new languages will have been exposed to different ways of doing things and different ways of looking at the common problems - something that someone who didn't learn anything except repeating their experience over and over wouldn't have learned.