Hello Everyone

I am graduating this May after 6 years in school. My parents had applied for the B-2 visa but the were rejected.
They did not even open the file, all they asked was my name and after entering my name in the computer the person said that sorry, we cannot give you visa at the moment. My parents are well established and all the papers are legit, bank docs, income, properties, etc.
Is it possible that they got rejected because I was in school for 6 years? Even though I have been in school for 6 years, I am in good situation. I have good grades and good record.
Should they apply it again?
Anyone has had similar situation?

Do you know anyone who graduated after 5-6 years and their parents got visa for graduation?