Unpredictable or random rewards are more addictive than a predictable schedule.
"There are free loot boxes that give you very little at all, and if you get anything of value it is almost always the least amount listed in the chances."
"When you complete any puzzle, what you get from that puzzle is luck based."
"As Rōblox is a platform of games (rather than a single game in itself), developers are allowed to do just that. If the title of the game you're playing ends with 'Simulator', you're definitely in one that does."