the main way it seems to help is for working in aquariums. MOST (but not all) will only let a mermaid be in the aquarium if they are certified. It can also be a great help for mers that do ocean underwater photoshoots, however I know a few really famous mers that don't have certification and do stuff anyway and it hasnt stopped them.

medically, I can't get scuba certified until I have a surgery I am on a waitlist for. But I have had huge success and it hasnt prevented me from a single thing, including being in an aquarium. I believe if you're going to be in the ocean a lot and going down deep then there's a lot of great overlapping skills you can get from scuba. If you plan to ever use a regulator or breathe off someone elses then yes, I would suggest scuba. But outside of that for me just getting water safety training along with free diving training (for breath holding) has been much more useful.

I feel like there's a big misconception about the importance the mer community places on scuba when super well known mers who do really public stuff, don't have it.

Not knocking it, I am someone who believes any skill aquired is a good skill to have just that if you're prioritizing, unless you fall under those categories I wouldn't worry too much. And even then... lol