I've never had a problem, and I've been hunting public since I was about 12. I think a lot of it boils down to implementing some common sense. I don't leave anything in my truck I don't want stolen. I actually DON'T lock my doors, because I don't want my window smashed over a phone charger or something stupid. I guess they could take my battery, but that's cheaper and easier to fix than a busted window! I also hunt from a $500 truck, so if it gets keyed or dented...whoopie doo.
There is one WMA near me I don't hunt. Scouting it, there were way to many shady characters cruising around at 2pm on a Wednesday in crapped-out cars or walking pitbulls for my liking. The syringes in the parking area were the nail in the coffin.
I did have an interesting situation last season. I was hunting a WMA in a different county. Way more people than I unusually share the woods with, and about 3 hours away from my house. A guy who parked about 100 yards away from my truck had a stand stolen out of the back of his truck. Apparently they hit several people on that road. I had a kayak on the roof, a bike on the rack, and some minor gear in the truck (it was a weekend trip, so I kinda had to break my rule). I reckon a kayak is hard to fit in a truck discretely, and the bike was locked.