Age of "new" tires

I may be a little short on new tire laws but I see no problem with outdated tires. I very seldom buy new tires because good used tires are easy to find for a low cost. I almost never have a tire problem with used tires other than wornout tread. I've probably only had more than ten flats in the 67 years I've been driving. If the casing is good and there is a decent amount of tread, I'm happy. If you're not driving at 70 mph or over in our old cars, whats the problem?