A reverse image search has a lot of limitations; however, an image search works great for discovering catfish accounts. This is due to the fact that a social media catfish account will often use a photo that was acquired elsewhere on the internet.
An image search works the best when searching by using an image that also exists on the internet:
Catfish accounts often use stolen images off the internet.
Think of it like this:
A photo has a good chance of finding its twin on the internet, or triplet and so forth.