>It seems to amount to a similar principle, that their business model depends on repeat customers, and would fail if they lost trust.
You think dollar general is making $37.9B (in 2023) of annual revenue from one-off customers? Unless you're operating a tourist trap, or some sort of business that people only need a few times in their lifetimes (eg. real estate agents), most businesses rely on repeat customers.
No, I think they have other advantages that are less attractive to me.
I have money to buy in bulk, care about quality, and am willing to make longer trips to stock up. The membership is trivial relative to annual groceries.
I think think the target market for dollar stores is the opposite
Note how they tend to have captive customers.
Dollar stores around here pop up in small towns, killing off any locally-owned competition, and are far enough away from the big chains to mean they can charge quite a bit more while offering terrible service.