The only times I've ever heard of folks RVs getting burgled, the RV was either in storage at a U-Store-It place, or in their own driveway or the street in front of the sticks 'n' bricks in town, or overnighting at a Wally World. In the 55 years since I first went camping with mom and dad as a kid, I've never heard of a break-in at a campground.
Not saying it never happens, just that I've never heard of it. I've not installed a security system as I deem the purchase thereof a greater risk to my wallet than burglary.
Oh, I do recall a single instance in a campground, come to think of it. Some teenagers from town came through in the wee hours one night as stole a guy's cooler full of fish, evidently looking for beer. And they opened our pass-thru storage compartment, but finding only a grill, chocks, wheel grease, hammer, etc. they moved on.