In some cities you would need a permit to replace an outlet. And only licensed electricians are allowed to get permits. In some cities bad wiring jobs don’t just burn you own house down, it’ll take the neighbors house with it. So it’s not just your butt on the line if you screw up.
People do that anyway, just that you'll have tough luck if it comes up in an insurance case. Or worse if you are in a condo and other people suffer.
Wiring and outlets are simple enough, but you wouldn't believe peoples' capacity to botch things up. They'd connect a ground pin socket in place of non grounded one without changing the wiring, or use incorrect section wire, or with incorrect insulation type for in-wall application, or they'd replace a charred outlet without trimming the sooted part of wire. Enough nuances to avoid amateur work.
But you can fix you or your neighbors outlets all you want.
The distinction is drawn at being a business vs yourself. But, we still have that individualist spirit, so I could be wrong about other places.