Final Fantasy 7 has a cast of 9 characters, but you can only take 3 in your party.

This means most of the cast won't see much play. Cait Sith is neither particularly strong or popular and while you can cheese an instant victory with his (rigged) limit break he isn't the only one with some exploits going.

In the end, people end up playing with whoever they enjoyed and Cait Sith was rarely the guy.