The issue wasn't the app exists and people were using it. It was the demographic this app was targeting.
The app was targeting 13 to 35 year olds. People under 18 has to get parental permission which was literally just selecting a box.
The $20 of free money is a big deal for a kid and they might not have the best idea of what they're giving away with agreeing to this.
It's a really scummy move and possibly illegal to target kids like this.