You can buy things from your local Amazon or national equivalent that come from outside using this systems, so, you are not so restricted to EU sellers.

I suppose the most problematic would be traveling. I recently when outside the EU and was surprise how smooth the process was using my Visa card, to the point I didn't use any local currency.

On the other hand, I recently buy books from the UK and it get stuck for two weeks in customs, and it had nothing to do with the payment platform. I had not realized how difficult is to import something from outside the EU, even for personal use.