Roblox has been trying to move away from being a game for kids, and more towards all ages.
Specifically, by verifying with their third party service and your ID (kind of creepy, but probably the only real way to still remain coppa compliant), you can access more mature experiences and use voice chat. And they're predicting that online daters will proceed to evolve into getting actual real life relationships.
Its not necessarily a kid's game, but that is their primary demographic and player base out of some fusion of being easy to run, simple games being easier to create, the art style, the accessibility and short term gratification of easily jumping between experiences.