Alternatively, they had full funding (even during the summer), focused on research and graduating (so it didn't take them 10 years), and didn't realize they needed to get an internship to be competitive once they graduated.
Even given unlimited research funding, to not once try working in industry (even during undergrad) betrays a worrying single-mindedness which I'd want to avoid in any technical hire. If all you do is proceed down one path, without ever trying anything else or being a little creative, I probably don't want you on my team.