Because there are ZERO regulations RV manufacturers choose the CHEAPEST way to do things. Believe it or not twisting wire ends and taping them would be more costly because of labor time. They would use SPIT if they thought they could get away with it.
Wire nuts are appropriate for things that do not vibrate or hit pot holes. Like a house.
Crimping is the way to go. When I crimp I use a hand crimper with a die that has a spike in it. FAR AND AWAY more secure than elliptical shaped crimps, and no, the point does NOT pierce PVC or nylon terminal insulation. Some myths die hard. Before doubters chime in with their moans, try it out before you commit to eating your words. Something in the formula of the plastic changed around 10 years ago and the die spike no longer splits the insulation. Try it for yourself.
