In Google Groups, if you allow people to request membership, you can have them answer a custom question (in the new Google Groups interface it's called a "New Member Question"). But the old Google Groups page for accepting pending members had a column title "Reason" which displayed the answer. I do not see any such column on the new interface and can't find anywhere where I might see that information.
2 Answers
The new Google Groups interface has a "Reason" column under Manage > Members > Join requests. I do not know when this was added.
I cannot find this column anywhere either. But you could review pending users under old interface (probably only in limited time, until new groups roll out completely). Just type this address:
https://groups.google.com/group/<your group name>/pending