Are you really going to equate a discount with what you're suggesting (rewarding purchases with amounts of anonymous internet cryptocurrency)?

A rewards system is to encourage customers to return to that same merchant.  If the merchant wanted to do that, they could just do that in-house and not have to deal with an alternate currency.

Cash back and discounts are to get customers in the door.  They're almost always temporary fixes to increase foot traffic.  And they're not in weirdo internet fake money.  Here's let's play out this scenario.  I'll be the customer who just bought a cake from your bitcoin-reward bakery.

"So how does your reward program work?"