Let me preface this by saying I do not use two hides and in some cases, I don't use any hides. It depends on the animal.
I keep all my ball pythons in a rack system in a dark room that doesn't get a lot of foot traffic.
The fact of the matter is that most people who are keeping ball pythons as pets are not keeping them the same way a breeder would. So why should we give them advice as if they are keeping them the same way? People come to this forum with questions like "Help my snake isn't eating, what can I do?". I assume you know the basics of ball python care. If a snake doesn't feel safe in its enclosure, it is unlikely to eat. Suggesting 2 hides is not some scheme in order to get you to spend all your money on hides. It is a suggestion that often leads to solving the problem.
I agree with you that ball pythons don't NEED 2 hides, but for new owners keeping their BPs in aquariums, 2 hides can mean the difference between a snake that eats and a snake that is stressed.