People use it for many reasons.
Kids use it cuz they can talk in front of adults without them knowing what's being said.
Some use it to hint to others without being obvious in front of others.
For instance, Person A says something in front of Person B that might be considered offensive. Person C is standing there and decides to warn Person A without being obvious in front of Person B. So, Person C says... "ix-nay hat-tay ind-kay of-nay alk-tay".
