Most of the products purchased in response to direct-mail advertisements would be purchased even without
Why this is right
This is one of those correct answers on Strengthen that makes way more sense if you already had the objection that it's countering. Some people may have objected to the original argument that, "Direct-mail isn't saving me a trip to the store to buy something I was otherwise going to buy. It's showing me these items I never even thought about buying until I got the direct-mail ad. Look at my figurines from Avengers! I would have never driven somewhere to buy these, but when I got a direct-mail advertisement I decided I wanted them and ordered them." For purchases like these, where direct-mail created a consumer desire that didn't exist before, it's not fair to say "direct-mail is better for the environment, because it saved you a trip to the store!" There was not going to be any trip to the store. We'd be measuring all the environmental harm of the direct-mail flyers for the Avengers figurines + the harm of the delivery truck that brought it to my house vs. the alternate world in which I never knew they existed and never bought them. That would mean that the direct-mail world was more environmentally harmful than the world without direct-mail. So since it would be a big objection to say, "most things purchased because of direct-mail wouldn't have been purchased otherwise", it strengthens the argument to say, "most things purchased because of direct-mail would have been purchased either way." To put it another way, the author was Assuming a Similarity between the Direct Mail world and the non-Direct Mail world: in both worlds, people wanted to buy items X, Y, and Z. And then she's stating a difference between the two worlds: in the Direct Mail world, you don't drive to get it. In the other world, you do drive. And that's how she's deriving the idea that direct mail leads to environmental benefit, but if we deny that initial assumption (if we say people would not have gone out to buy this otherwise), then her argument doesn't work any more.
Skill tested: Strengthen · how this choice captures the argument's function is the move to repeat next time.