Watercooling has 2 uses :
Silence : No sound builds , passive cooling systems , big radiators , it's an expensive setup + to have a pump that makes little noise. Ofc this wont be very good for ocing , you pay a LOT of money just for it to be silent.
Extremeocing: Big radiators + fans , usual noise from fans , but it's expensive.
Now there is a third watercooling choice : The premade builds. These are somewhat cheap builds ( still more expensive than air cooling ) that have fans , make noise , and are worse than an air cooler of the same price.
If you choose 1 of the first , you pay up a lot , that if you invested in your machine it would be better. So basically a new machine with an expensive wc , even heavily oced would get worse performance than a guy that just gave the same money for a better system with an air cooler.
The thing is , if you check for coolers ( both air and water ) and put them side by side from price ranges , Air allways wins ( more cooling power for less money ). And to make a custom wc rig takes time/money only advised for the people that really love it
TL;DR : Air cooler have a better performance/cash ratio, and to have a wc with better performance ( read custom ) means giving a LOT of money that would be better to be invested on the setup itself.