The technology allows them to hold up to the centrifugal forces, but they can’t stand the heat.
Every time a car goes down the road, the tires heat up. They cool back down when parked. These hot-cold cycles cures the rubber a little more everytime. over thousands of miles the tire gets harder and harder. Thats why an old tire that still has tread loses grip.
At these extreme speeds, the technology is not far enough along to make the tires stay soft. They are over-soft to start with and harden very quickly at those extreme heat levels. A drawback to the softness is treadlife. They would rather the tread wear off that for the tire to harden, lose structural integrity and fail at 200mph.
Hmm...I'm trying to envision a catastrophic tire failure at 200 mph in a passenger car. The pictures I'm getting aren't pretty.