Why would tire manufacturers love this? Certainly retail stores don't like it because they have to either slip those in on people who don't check or offer a discount to those who demand recently made tires. I would assume, there is push back to manufactures if retail stores are getting stuck with old tires.
How much impact is likely open to debate but if you've ever been close to a new tire, you can smell it. Just like "new car smell", that's off gassing of polymer compounds. Those compounds help define the physical properties. This occurs even in a dark warehouse away from UV.