The movie didn't make it out to seem like its because he's royalty. If he was royalty and already knew about the abuses then when he's there they wouldn't care if he sees people walking around looking down, tired, or worn out. So long as he's not socializing with them it would make no difference to him. I'm pretty sure its to hide what's really going on, but that's just my interpretation based on how the movie made it sound.
Also remember the movie made it clear that the they try to prevent members from going online or reading any external articles on the cult. I have no doubt that there are people around Cruise at all times trying to shelter him as much as possible.
My personal opinion at this point is he cant leave even if he wanted to. Another thing to consider is his entire family including his 80 year old mother, his sisters, and now all his kids are members so if he did try to leave he risks a chance of them not talking to him anymore which I dont think he'd risk under any circumstance.