Most of the time the guy will be too fucked up to gather his senses and stand up and the ref will need to stop it. If the ref doesn't stop it the guy who just got fucked up will have to stand and bang with you. There is literally zero reason to follow someone to the ground to finish them off. It's also a baller move which make you look better for the judges in case the person isn't finished.
I just rewatched coyboy Oliveria vs Ryan Leflare and Cowboy punches him and walks away and the ref has to stop the fight even thought Leflare is squirming around. If Cowboy hopped on him it would provide an excuse to not stop the fight.