I think it depends on the length of your rig and the placement of your power cord inlet on the camper.
On my old 42' rig, the power inlet was at the rear corner. I only ever had 2 or 3 occasions in 5 years (1000+ nights and probably 150+ campgrounds) where I needed an extension cord or could have used one.
On my new 44' rig, the power inlet is mid-ship. I have had the camper for almost 18 months now and have needed an extension cord probably a dozen times.
I actually really like Old-Biscuit's idea of putting in a second power inlet onto the camper. If I recreate that rear corner inlet, it should alleviate the need for ever needing an extension cord.