If they tested explicitly for piracy tools (e.g., looking for A**S***), I could understand them. But why not run on a device of a legit(!) jailbreaker without any pirated software - this is what I can't udnerstand. After all, iOS is far less usable without jailbreaking: f.lux to make the screen's white balance much better and warmer, Quasar, Safari Full Screen, mouse support, Skype / screen recorders, Springtomize, WebOffline, Infinidock, Airblue Sharing, being able to use external storage cards as true storage memory from AppStore apps etc. All that would be non-existing without JB.