Cars get scrapped for many reasons and might not have anything to do with the battery pack. I don't know if you have ever heard of junkyards, but people have been going to them for years to get perfectly good parts from junked or totaled cars. The average age of Japanese vehicles is only 9 years old. Most people don't drive cars to 150,000 miles and beyond. If Toyota is using the batteries from older cars, that by definition means they were still useful batteries on those cars.
I really don't know what to say about your 1990 vehicle comment. Good for you? Just because some people own a classic car doesn't change the fact that more than 99% of classic cars are scrap metal now.