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.
The new Google Groups interfacewhere is the pending members' answer to custom question
google groups