"This is, incidentally, a chief reason why pure market solutions"
Yes, but what is a "pure market"? I like to believe that my local home improvement or grocery store has some kind of concept of their own brand and puts some effort into getting decent products on the shelf, whether store brand or not. So, I hope that their markets are not as "pure" as online sites where anyone can sell.
You might read "pure market" as "self-interest seeking", as opposed to some entity acting as a regulator in the public interest.
In the case of a brick-and-mortar store, part of what the retailer is paying is for a physical retail location, which you might think of as access to a specific cohort of local traffic (foot, vehicle), and customers, in the sense of patronage of a retail establishment by custom (https://www.etymonline.com/word/customer).
Since that is a finite set, and there are often (though not always) competing retailers, practices which alienate customers tend to be counterproductive.
I was actually thinking of the local B&M hardware store where the staff know their products, and customers, and I've been making a series of (to date, satisfactory) LED bulb purchases whilst writing my earlier comment. What is ultimately carried is a function of the store's specific traffic, the parent corporation, and other arrangements (there are periodic government and utility incentives for low-energy bulbs), but the local staff and management have some agency.
Existential Comics' "Freedom Monster" thought experiment is worth consideration:
Yes, but what is a "pure market"? I like to believe that my local home improvement or grocery store has some kind of concept of their own brand and puts some effort into getting decent products on the shelf, whether store brand or not. So, I hope that their markets are not as "pure" as online sites where anyone can sell.