Just some napkin math, based on VIN's, there were about 250,000 ish total number of Model S's and X's produced with FUSC that is transferrable to new owners. I'm not going to count the non-transferrable kind, where it's only for length of ownership, and not life of vehicle.
Thats based on approximately 225,000 Model S's built and ~25,000 Model X's built on or before Jan 15th, 2017.
Again, approximate numbers based on VIN's I've recorded.
Factor in Totaled vehicles, traded in vehicles that have been stripped of supercharging. The number of FUSC vehicles is what I'd consider, fleet wise, to be rather small. I'd give a rough worldwide estimate of 200,000 or less with FUSC for life. MOST people don't use it a lot, some like me, do considerably.
I know utility costs have skyrocketed in recent months. I know we just got a double digit % increase here in Wisconsin, while at the same time, solar buy back was cut in half.
I think it's the pain caused by the usual state, California, and the absolutely out of control utility pricing (among other pricing there) that is causing a lot of the trouble.
Since off-peak rates alone in California are considerably higher than our ON peak rates in Wisconsin, which are already high, I know first hand as I've seen it, people who can charge at home camping out at superchargers. This is "unofficially" one of the reasons FUSC went away. Yep, Californians.