In the US Costco, for credit card payments in the store or fuel pump, only accepts American Express. Cash, checks, and (I believe) debit cards are also acceptable in the store.
Much rarer now that Costco is switching to Visa.
Since my dad mostly has high volume purchase (and only one or two a day) the 1.5% can mean a lot. He also says doing business with AMEX is hard (if there was an error) because he gets ridiculously few purchase and they don't consider him valuable enough. And everybody who has a AMEX CC in Europa has a Visa or master card as well.
That does seem to be true mostly. Shop near has the opposite though - Amex card use is free but for Visa & Mastercard there is a surcharge. Thought that was a bit weird.