App store “rules”

I notice numerous games in the app store don’t have to follow the official guidelines. (Example: “Children’s” games featuring perverse bodily harm, death, domestic abuse, etc…rated 4+)

Since there’s no easy path to report content, I assume these discrepancies are known and allowed.

Is the popularity, income, or fee for entering app store what changes these allowances, or something else?

In short, who/what decides which apps have to follow the store guidelines and rules?