I'd never ever shop at Sams, but why won't they accept Visa? What other CCs do they disallow?
I guess these large warehouse clubs can get special deals with credit card companies to lower their expenses per transaction. And I guess that Visa just said No to that deal.
I mean, look at Costco and their odd deal with Amex, which is the only credit card accepted there in store. You can use Visa online, though, similar to the differences between Sam's Club stores and online portal.
I used to have a Costco membership a couple of years ago, & they did actually take my Visa. Is it a recent thing that they only take AMEX? Perhaps it is not across the board.
That's a general policy nowadays. You can use Visa online, but in store, it means cash, debit, their own "Costco" payment cards or Amex. That's why I have that Costco TrueEarnings Amex.