We call it "fish and chips" because the meal Fish and Chips is beautiful and simple but not very notable, just like this type of conversation
RandomUser1 (10:00:00 AM): glad we talked about that
RandomUser2 (10:05:00 AM): yeah
RandomUser1 (10:20:00 AM): mhm...so uh...
RandomUser2 (10:30 AM): haha
RandomUser1 (10:45 AM): I'm tired...
This is an example of a typical AIM "Fish and Chips" conversation