What makes them illegal? I imagine the only reason nobody does it is because there’s no market - anyone that wants their phone jailbroken probably doesn’t want to pay, or just doesn’t want to be without their phone for a week+. Plus, it’s not like a commercial operation like this is going to start making their own jailbreaks and then hoarding the exploits so that you can’t use your own PC to perform them - the jailbreak community would immediately hate such a company.