I've recently started reading an interesting superhero fiction series called "Wearing The Cape" which discusses aspects of registration in a world where superpowers suddenly appeared a decade ago in a world that was normal before then.
When that event happened, governments around the world reacted in different ways. Some were more accepting of the sudden presence of superhumans and some were harsher, trying to kill any they found. In some areas of the world, there are wars still being fought by different groups for control of those regions and many governments collapsed overnight.
Registration came about in that world's version of the United States as a means of helping normals accept people with powers, because it was terrifying to them to suddenly find themselves living in a world where the police and army were now supplanted by people who didn't have to listen to the government if they didn't want to. One of the first and most powerful superhumans, Atlas, in order to try and put a friendlier face on his kind, put on a homemade superhero outfit and went out helping people in trouble and assisting where he could. Others followed his example, kind of like how DC had Superman as the first superhero.
In that world, superhumans in the United States work as part of an auxiliary force assisting police and firefighters. Not everyone wants to "wear the cape" though, and many superhumans try retain their normal lives after experiencing their empowerment event, if they still look human. Some people change too much to be recognized as human when they become empowered.