Samsung Pay's new shopping service is good but we can't control how we sign in. I am VIP customer in gmarket ( i get extra discount coupons) but new id forced by samsung pay doesn't have that facility.
additionally, I generally use a different email id for online shopping to avoid getting frequent emails to my primary email address. While samsung pay is registered to my primary email address i started getting shopping related emails (i really hate this)
I hope if samsung allows users to edit login details (similar to accounts in Android settings) or ask to choose between sign in using preexisting details or auto signup then users would be more tempted to use samsung pay's shopping service.
To give you a better service may be ask you to provide your Name,Samsung Account, Gmarket ID through "SamsungPay App → more →Contact us → Ask Questions"
