It's for the same reason a gun has to be unloaded. They don't want you hunting from a vehicle.
Law seems fine to me.
Gun does not have to be UNLOADED......just nothing in the chamber in a vehicle. Magazine can have shells in it. Muzzleloader can be loaded to fire EXCEPT no cap or primer can be on the nipple or powder removed from the flashpan. On an OHV the gun must be in a hard or soft, fully enclosed case and in a firearm, nothing can be in the magazine or chamber. The curious thing is that the regs really don't spell out if a muzzleloader is considered unloaded on an ohv if it has powder and bullet in the barrel and nothing in the ignition area.
Cowboy Action Shooter; Endowment Life Member-NRA
The Original Rocket Scientist-Retired
"My Father always considered a walk in the mountains as the equivalent of church going."