I was helping my neighbor move a shed roof last weekend. I towed my flat deck snowmobile trailer over with a quad, backed it up and we loaded the roof. It was a bit on the heavy side and I wasn't comfortable heading downhill with it so we decided to use their pickup to move it. Their 2wd couldn't back up (uphill) to the hitch. It couldn't even back off the driveway. Could we have "gotten by"? Sure, if we wanted to push, get a dangerous run at it or use a come-a-long to pull the truck to the trailer.
It was much easier to get my 4wd truck, click it into low range and idle back up to the hitch.
So yeah, sometimes you need 4x4 to tow. :W