Since running vehicles with run flats I've suffered just one puncture and that's in 50000 miles or 5 years. On that occasion the puncture must have happened locally as I parked up as normal with no signs of a puncture, in the morning the tyre was showing as deflated before I even got in, when I put the ignition on the sensors picked up the loss of pressure and "alarmed".
I drove the vehicle just over 500m to the local BMW dealer and it was sorted "free of charge". The tyre was totally deflated and the seal to the rim was broken, hence complete loss of air, they say you can drive "carefully" at 50mph for 50 miles, that is effluent from the bull! In my case to drive damage to the rim was avoided by driving very slowly, hazard lights on, etc.
They can and do repair "run flats" depending where on the tyre the "deflating object" is found. I like run flats, but I've driven most things including vehicles without tyres, however the problem is annoying and like Brian I can see it's done for cost saving, fuel efficeincy (more effluent from the bull) and to rip off the customer.
Just my thoughts