It's up to the merchant to reward the customer for using BTC, which is well within their capability to do (and some merchants do... like Gyft)..
When credit card companies give you 1.5% cash back, they are giving you 1/2 (or less) of the extra money they made the merchant charge you back to you.
If a merchant can accept payment in bitcoin, then they can charge 3% less (generally) and still be ahead on the costs of accepting credit cards (because there are no charge backs or credit card fees for them to worry about).
It's pretty well established that the overall cost of the credit card system is much higher than using bitcoin. There's normally a much higher disparity than that for remittances as well, which is another area where bitcoin can really help..
If you read some bitcoin FAQ's or watched an introductory video or something, you'd know all of this already.
You've said it all there. Kudos for educating the OP