Wrt. stuff like SEPA there's even more incentives:
D) Strong Integration-forces at the EU-level:
Especially amongst the founding members (Belgiun, France, Italy, Luxemburg, the Netherlands and the FR of Germany (formerly "Western Germany")), the EU is still more-or-less seen as one of the two pillars guaranteeing European peace (the other being the US (& USSR as a common external threat), which sort of acted as
"the impossibly powerful aliens" that made intra-European squabbles look increasingly provincial and petty).
"Not going back to the bad old days" still carries a lot of currency in many EU countries.
E) The normative forces that accompanied the standardization implicit in the European integration process - "
You want peace & prosperity - then you'll put up with us standardizing the curvature of Bananas (and the banking system)" Compared to standardizing Bananas, the standardization of the banking systems looks positively ...
"not bananas at all" ![trex :mrgreen:](https://forums.questionablecontent.net/Smileys/qc/trex.gif)
F) Intra-European travel & labour: The contemporary EU (including UK) has a population of some 510 millon people (157% of the contemporary US) living in
half the land area - 116 vs 35 people/km^2 - divided between
some 28 countries. So travel & working abroad is easy & attractive ... when national bureaucratic hurdles are removed. In the mid-20th Century, it was mostly mediterraneans who worked in the north-western EU as "guest workers", today it's pretty much everybody.
When I visited my parents while I was living & working in Antwerp, I'd travel 260km and cross two national borders (Belgium/Netherlands/Germany). It's not just
"polish plumbers" (*) who find the four freedoms attractive - German physicists completely agree!
European standardization may represent a fatal lack of national autonomy to folk like Le Pen - for many, many Europeans, starting with Gen-Xers (Macron's
"Generation Erasmus"), it simply means
"less bureaucratic insanity".
(*) I also fail to see what's so terrible about polish plumbers - my cousin-in-law is a naturalized German, born in Poland. She's also the hairdresser I trust ... ![grin :-D](https://forums.questionablecontent.net/Smileys/qc/grin.gif)