If I remember correctly I had some vague knowledge that basically anyone can own an ATM and set the surcharge as they want. I probably looked into it as a passive income stream at some point (these things had a high growth phase some time ago). Then I think the first time I heard about ATM rebates was on an advert of some sort and the whole thing seemed obvious. So I looked into the fine print and it seemed to check out.

I don’t think this was ever a thing until online banks came around during Web 1.0 , traditional banks would charge you a fee for using out of network ATMs (which is still pretty standard), but the online banks resorted to offering surcharge rebates as a way to compete with brick and mortar banks. And also to overcome the obvious pushback of people wanting quick access to their cash. Then smaller banks started offering it as a way to compete with the national banks that have huge ATM networks.