Because they bought out LoopPay. But what they failed to take into consideration is chip cards - this method does not work with cards that have chips. All of my credit cards have been upgraded to chip cards and more and more retailers are updating the POS systems to refuse a swipe from a chip card in favor of inserting the card instead. ApplePay still works.
LoopPay was great when it started, but chip and pin is going to be its demise. Samsung was a day late and a dollar short.
Actually it does not matter if you're using a chip card or not. I have Samsung Pay with 2 chip cards and I've paid with Samsung Pay flawlessly with both of them at multiple retailers that require chip cards currently.
The secret is that Samsung Pay does not actually transmit your credit card number, and the banks allow Samsung Pay transactions to happen with magnetic readers. The transaction is tokenized, so even if someone perfectly captures the card number with a skimmer, they can't get anything useful out of it because the card number transmitted will be rejected after it's used once (the only hole there is someone could send the transaction before the merchant does, but that would be pretty obvious as Samsung Pay gets a push notification about what store charged you and for how much).
And also, I am not aware of many card readers out there that don't have magnetic swipes at all, so Samsung Pay is still going to be useful well into the EMV age. In addition, Samsung Pay does indeed work with NFC, the same technology as Apple Pay and Android Pay. So as far as I can tell, Samsung Pay will indeed work with NFC, same as Apple Pay, and indeed work with more card readers (most card readers, even) than Apple Pay can (and Android Pay for that matter).
But in complete fairness, there are some downsides. You cannot use it with gas station pumps or ATMs. And there are indeed fewer cards working with Samsung Pay than Android Pay. I have 2 cards on Samsung Pay, and 7 cards on Android Pay (yep, I use both of them, concurrently). At restaurants or small businesses, if they take your card and swipe it, you should just give them a card, you don't want to tie other people up because they won't know how to take your phone and put it on the reader and get it to work, and Samsung Pay only allows about 10 seconds to get a transaction running, which means you would have to reauthenticate if it didn't work the first time, and just generally don't be a dick and make an associate have to do stuff they don't know anything about, and tie up the line behind you, things like that.
Ultimately though, i think it's not a terribly big deal, I still need to buy gas, or even get cash at the ATM, and I need my cards (and my license for that matter), so carrying around my credit cards is just necessary still. Fortunately for Samsung, MST is good technology that will work in places where NFC will not, bad for Samsung is that when NFC is at 100% penetration then people won't need Samsung Pay and they could buy any other phone and get the same functionality. Oh well, it's just kind of how things are.
