When we had our trailer having 4wd made it a lot easier to back up to our trailer to hitch up. I wouldn't have to touch the gas at all - just lift my foot off the gas and roll slowly towards the trailer. Could I have gotten by without it? Definitely. It just made things easier. Other than that there were a couple of times where I needed it to help get out of some wet campsites. It's nice to have when you need it.
Something else to keep in mind is that down the road a truck with 4wd will be easier to sell.