Your analysis is spot on. All we ever see are "where can I get the lowest price on XYZ product."
Suppliers who work on wafer thin margins must necessarily make their profit somewhere - this is usually by spending as little as possible on after sales service.
It's also pretty evident that many businesses seem to think that a good sales and marketng plan is all that's required - and to get going, it can work. Proper business plans include a well thought through after sales plan.
I susapect the eventual answer may be that the retailer simply does not do after-sales - they can discharge their responsibility adequately by relying on manufacturers more and more.