Monopolies can benefit the consumer, at least in the short term. When Netflix was the streaming monopoly, it had more popular content at a much lower price. Competition between streaming platforms has resulted in better deals for studios selling streaming rights to their content, but a much worse deal for the end consumers.

Similar deal with Audible, their monopoly on audiobook sales leads to really good deals for their users, at the cost of terrible payouts and cut percentages for authors and publishers.

To be clear I’m not saying that monopolies are good, but saying they never benefit consumers isn’t quite accurate either. As a storefront you can use high user counts to force better deals, which helps retain users and block out competition.