Those of us that travel regularly out West know that there are many areas without cell service and some places that are over 100 miles from the nearest GAS station, let alone a tire shop that stocks RV tires.
The decision to carry a spare is a matter of choice. Most of us that do carry one hope that we will never need it.
You don't need a spare as long as you have a back up plan, that includes ERS, a toad to drive to find cell service, and a major credit card. You will eventually have your flat tire changed, no matter where or when it happens. Carrying your own spare, even if it is unmounted, may save you a lot of time at the side of the road, as well as a lot of money.
Of course even if you do have a spare, you still would have to hop in to your toad to find cell service, or, if you are willing and able, change the tire yourself. There are always choices. :B