Thieves will just cut it, I’m amazed they took the time to unzip your brothers. I always left nothing in my Jeep and the doors unlocked.I think it's for security. Seems like you can't slide the windows out without opening the tailgate/doors. Granted someone could just take a knife to it if they wanted in, but my brother had a TJ with a zippered top and someone just unzipped it and stole his cd collection. This at least makes it a little more difficult to get in.