I drove a RWD Xterra for 11 years. As others have said, it depends a lot on where you live and whether you go off the pavement. For the most part, my X went everywhere I wanted to go but there were a handful of instances where I desperately wished for 4WD. For example, December 19, 2011 (not that this is etched in my memory or anything) when an ice storm hit metro Atlanta.
My commute was 38 miles (from near Waleska to Alpharetta if you know the area) and usually took 50-55 minutes. I headed home at 6:55pm and got there at 1am after my wife had to come get me in her FWD Acura. I got to a place where the RWD just wouldn't go up an icy hill. (I wish I'd thought to try airing down but it probably wouldn't have mattered.) For the record, her car got stuck too a mile from the house and we walked from there, which took a very long time because of how slick the ice was. In fact, I wish I could take credit for the maneuver I pulled off right before we abandoned her car but in truth it was sheer desperation.
We drove past our next-door neighbor's abandoned truck, which was half on the shoulder. The hill was ridiculously shallow but like the owners of the many empty vehicles there, we couldn't get to the top. We started sliding backwards toward the neighbor's truck. I was turning the wheel to try to avoid it but all that did was get us sideways. I said, "We're going to hit Don's truck, there's nothing I can do." But then it occurred to me to pop the car into R. I did and tapped the gas and it got us going enough that we missed by a foot or so. The car continued rotating until we'd done a 180 and were able to drive down the hill and park in a pasture where the residents had thoughtfully opened their gate so people could get off the road.
A sidenote about my neighbor Don, the one whose truck we almost hit. He was in his 60s then (he's since passed away) and a real cowboy - literally, he had worked with horses all his life. Tough as nails and he and his wife were the nicest and best neighbors anyone could wish for. I asked him later why in the world he had been out in that storm and the answer was pure Don. One of his clients had called because their horse was seriously ill. Its only chance was a vet specialist at the University of Georgia in Athens, which is 95 miles one way from our subdivision. Don had driven the horse to Athens to try to save its life. He was awesome.
What were we discussing? ;-) Seriously, for people in many places, 2WD is fine, but when I sold the Xterra, 4WD was a must have in the new vehicle both for weather stuff and b/c I wanted to do much more offroading,
which I have. 