eBay is not made with the Canadian market in mind.
USA has cheap tracking. Which means almost everything is sent tracked. If something doesn't arrive, there is a genuine issue. From that perspective, an automatic case streamlines things for the buyer because they don't have to know how to navigate eBay, and they do not have to send out multiple messages.
In Canada, most INR cases are because of lettermail delays. While opening an INR automatically streamlines things at first, it creates a big hassle in the long run since the buyer's item almost always arrives eventually. Once a case is opened, a seller has to refund by the deadline or risk getting a defect. Because delayed lettermail items often arrive after the deadline, this means the buyer and seller have to jump through hoops so that the buyer can pay a second time to re-imburse the seller for the refund.
The best thing you can do as a seller is to set up your listings with the generic "Economy Shipping" option instead of "Canada Post Lettermail". If I recall, Economy Shipping tells the buyer their item will take as long as 18 business days. For example, if I sell an item in Canada right now the buyer is told it might arrive between the 6th and 24th of June. This gives them a more fair and accurate expectation of when their item might arrive. Most lettermail items arrive in a week or two, but in very rare circumstances they do get delayed 30-40 days.
eBay's lettermail shipping option assumes that Canada Post's 7-9 day window for lettermail is accurate, when it is not guaranteed. A buyer who might not buy a lot via lettermail sees an expected delivery date of a week and a half, and assumes their item is lost or mishandled when it hasn't arrived by that time. That's why a case gets opened.
