Why not offer free shipping for ACEOs?

I’m a (currently) obsessive ATC trader and ACEO purchaser living in Canada. I notice most people sell their ACEOs on eBay, and that a majority of sellers are either in the US or UK. Among these, some offer free shipping, but most seem to use eBay’s shipping calculator and charge anywhere from $3 - $18 USD for shipping. Or worse, they don’t offer shipping outside of the US or UK at all.

As a veteran Etsy seller (though not for ACEOs), I know shipping costs are a huge disincentive to buyers considering a purchase. ACEOs are so cheap to ship — usually just the cost of an international stamp. Why not offer free shipping, cut eBay out of the shipping racket, and add the cost of an international stamp to the minimum bid for the ACEO? I feel like sellers would make MANY more sales that way! (You’d certainly be selling stuff to me all day long these days 🤣😆).