UK/EU has had contactless payments via our bank cards for about 2 decades now. America caught up eventually some years later
When phones got the ability to act as our bank cards, it made sense for them to use something compatible with the same technology that was already deployed
Funnily enough, America (and I guess also Korea, given the companies) dragging their heels on standard contactless is one of the main reasons why Samsung/LG briefly put out a couple of generations of phones that had a magnetic stripe mimicking payment feature in addition to standard NFC (https://en.wikipedia.org/wiki/Magnetic_secure_transmission)
I'm tall because ham?