If it mattered enough to be commercially viable, they totally would be. Actuaries are ruthless.

Since this is not happening, we can infer that insurance companies believe the benefit to their risk profile is less than the cost to administer the program and issue discounts deep enough for customers to participate.

It seems counterintuitive that stopping distance is not that big a deal, but it must be true.

Certainly it would be cheaper for them to run a program where you take a photo of your tires every few months, vs. the program they all have where you plug a surveillance device into your car. So the true benefit from good tires must be far less than driving style.