I've been on this forum for a while, and can't remember anyone saying the hitch was stolen from their truck. Many have a cover of sorts over the truck bed, when not towing, as I do. Of course out of sight helps, but I have never once thought, I hope no one steals my hitch.
Like you said, it is so darn heavy, just not an item to grab and run, or even toss into another waiting vehicle.
If you often park in places/areas, where crime is high it may get stolen. In this case, the entire truck may be stolen/towed off.
IMO, don't worry about it!
Jerry