Congrats on the Sams store account!
Virtually all of the co-branded cards state that if the credit doesn't meet standards that they will consider you for the store-only card, or a card with different features.
There have been offers to upgrade, but they seem hit-or-miss. I was even prompted once for an upgrade at the register, but when I said I'd accept, the offer wasn't valid, and after a run-around with customer service telling me I needed to fully apply for a new account.
I've had my Sams store account for years, and as others have pointed out, there are the promotional financing offers, and the ability to get $60 back at the register. I sheepishly admit that more than once on my Wally and Sams cards I have gone into the store and bought something (anything) just to get the cash back with purchase. If the item is cheap enough, like a $2 tool from the hardware department, it's cheaper than a standard ATM surcharge.
I was going to garden... Honest!