I think you will find that car manufacturers have a great deal of inertia - they are very slow to react and when they do react, they tend to take baby step.
Case in point: Firestone / Ford. It was obvious that most of the problems occurred in AZ, CA, NV, TX, and FL. So in response, did the car manufacturers specify higher temperature rated tires (higher speed ratings)? Well, sort of. They realized the general public seems to think that the speed ratings mean the absolute maximum speed the tire can withstand - that the general public thinks that means they only need a tire rated for 85 mph.
So what many of the car manufacturers did instead was specify LARGER tires - which is also better, but is a small step compared to a speed rating change!
But some actually did increase the speed rating specified. But the problem here is that the general public tends to want cheap tires and AZ, CA, TX, NV, and FL are no exception - and that means S and T rated tires.
Personally, I think these states ought to specify at least H rated tires for the safety of the buying public - but if car manufacturers have inertia, government is even worse!