It's just natural attrition.
The are all over 10 years old now.
Most have over 100,000 miles, trashed seats, too many young owners thrashing on them, or are slowly rusting away.
I still keep up on the classifieds around LA, there are always several SVT's for sale at any given time, very rarely does one come up for sale that isn't about due for a complete restoration. The few decent looking ones are priced at $8,000+ for a 70,000 mile, 12 yr old Ford.