You'd be surprised at how easy someone can get into your car without a sound. Now a days, people don't flinch at the sound of an alarm going off, not even their own(unless recently a victim). One of my coworkers has a MegaCab Dodge(sick lookin' truck) and the windows are **** near impossible to break(some layer or coating to help prevent breaking) and he has a top notch alarm that turns the truck on and off, pager feature, etc. Guys tried breaking into it around 11am MID DAY! You can see where they took multiple shots with what looked like a bat to the window. He never rose to the alarm as he was passed out.