While we may make most of our payments within EU, basically everyone still occasionally pays for something outside of EU, either online or when they travel. This means if the new thing only works in EU, every European will still need and have a MasterCard/Visa even if they use it less often than before.
This is still a massive amount of leverage - MC/Visa still have the ability to block payments made from EU citizens/companies to outside.
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.
The big benefit is that all internal EU card transactions are no longer routed via US companies which is quite ridiculous.
its not exclusive, but there is a problem with network effects. From the point of view of a business why should they add support for a new payment system no one users, from the point of view of consumers why should they sign up to a new system that no one accepts?
As I said in another comment the most likely alternative is a more decentralised system that all countries/currency blocks that want sovereign payments can get behind.
If there were an EU card system id certainly sign up for it and demand from vendors that they support it. I don't want my data ending up in America especially these days.
The network effect will work out fine because we have reasons to want it.
Network effects are very powerful.
You might care enough about privacy but most people have given up.
It is majorly used for debit cards, and similar in use to the famous Minitel in France.
You can use it to load pre-pay phones, or other kinds of rechargeable services, buy tickets for public transport and various kinds of shows, pay water, electricity, taxes, among other services.
There is now an app used to pay on shops via QR codes.
You can also pay online with one time cards, that are generated for a single transaction.
Outside Portugal it is a regular debit card.
When you access Multibanco with foreign cards, you can only withdraw money usually.
That said, I love MB and MB Way. What an upgrade it's been over paying for stuff in the US (where I lived before moving to Portugal).
I was buying tickets on MB, before it became common place in the Internet.
All the stuff I'm familiar with is only payments (with entity and reference).
Now that I think about it, you could search for things on Minitel but I don't remember if payments were made as phone charges or if they could also be done with transfers.
Minitel was so prohibitively expensive to use (just about every service cost multiple francs per minute), I didn't do much with it.
https://immolusitania.ch/the-real-deal-with-atm-machines-in-...
It works for the purpose to pay something online.
If you want an example, Eurowings.