It's the classes.

Roblox sells classes as a type of tech education after school activity, where they teach kids to build stuff in their game engine. Parents like it because they are often worried that regular school curriculums don't prepare their kids for a tech centric economy. HOWEVER, the material for these classes are entirely un-subtle about the prospect of making money.

Even worse, the game will guide you to spend in game currency advertising your game.

It's using the same dynamic as a multilevel marketing scheme on children.

Disgusting