Interchange as a standalone might be low but scheme fees are about the same nowadays. Aydens provide a detail breakdown per transaction, for example on a UK consumer credit card there's sometimes 8 different line items (interchange, ayden markup, various scheme fees), one generally does not get out under 0.5% on interchange++ even in the UK on the most favourable cards. When you're on interchange pricing with either Stripe, Adyen or another big boy you're paying extra for AVS, 3DS, and several other scheme services. No one is walking away with 0.2% all in. A lot of people find these Visa and Mastercard published PDFs for interchange and think that's cheap, but reality is when the schemes got their nuts tightened on interchange fees they just spread the loss by marking up various scheme services and mandating them. John still want's his Avios points even in Europe/UK.

The gov.uk runs card transactions for dozens of services - which add up - from car tax, driver license renewal, passport replacements, to paying previous NI years (do you consider this tax?) and so on..