It occurs to me to wonder; if you are driving a pickup or SUV, and towing a trailer, 4X4 is either an absolute necessity or "just good insurance, better to have it and not need it than not have it and need it", but if you are driving a motorhome of any type (A,B, or C) and towing a vehicle, 4X4 is not only unnecessary but it is a foolish expense to have it installed. 4X4 conversions for nearly any motorhome are readily available, but seldom does anybody say "You should have that thing converted to 4X4, you might find yourself stuck on wet grass or in sand!"
Of course, then there is the fact that the "just good insurance...etc." statement can be (and often is) made about other tools (which I won't name; it causes too many people to freak out), but it is just as logical in that application as it is relating to four wheel drive.