https://www.cnet.com/news/samsung-pay-what-you-need-to-know-faq/
"Samsung Pay uses near-field communication (NFC) technology to process payments at tap-to-pay terminals.
However, the system also works with almost all other magnetic stripe terminals as well. These older systems are widely deployed throughout retailers in the US. Samsung Pay uses magnetic secure transmission (MST) when the phone is held against one of these registers. The phone emits a magnetic signal that simulates the magnetic strip found on the back of a credit or debit card."
And even if its adopted in the US,it will be a century till third world countries adopt it so Samsung still won
As kdarlinng suggested its not a bad idea to buy a Samsung phone purely dedicated for purchases unless you want to be that guy who is fiddling with the credit card in queues