Other measures indicate similar concentration in roughly the same places (excl. maybe China), such as a light pollution (indicator of energy usage): https://www.lightpollutionmap.info/
China obviously, there's not much they wouldn't just buy on domestic platforms using domestic payment services, but almost all of Asia is pretty dark on Shopify, compared to your map. I guess they're just not a thing there, plus maybe black friday itself. Also, the UK is disproportionately brighter on the Shopify map compared to the rest of Europe. Interestingly, light pollution seems pretty low in Germany compared to the Netherlands, but in Shopify it seems to almost be the inverse.
Definitely a factor, but Japan and Hong Kong were going pretty strong compared to the rest, so there's at least that. Would've expected Taiwan to show up in a similar fashion, but also almost nothing there.