I think it's because the parent would expect a job offer instead of an internship.
It sounds like he only found XSS, which isn't exactly worthy of a job offer anyway.
1) XSS is game over for sites with authentication. What kind of vulnerabilities do you think are more important than XSS?
2) XSS is a result. There are a lot of complicated XSS bugs.
I would've loved an internship as a new high school grad... most people don't get a tech internship till 2 or 3 years into college.