Why not just keep prompts for say 6 months and punish users (they can all be identified because they pay for subscription) if they ask it to generate something

Why not just keep prompts for say 6 months and punish users (they can all be identified because they pay for subscription) if they ask it to generate something illegal? I believe that the system should be punished only if the prompts did not ask for anything wrong but it did end up generating i.e. sexual hallucinations, so to say.