They will have a lot of frustrated customers if they are the last to come aboard. It's like a place that only accepts cash.... sorry, but I don't shop at those places because I don't carry cash!
In a few years people will just not carry their credit cards. And when someone says "sorry we don't have NFC!" I'll say "sorry, I don't carry credit cards anymore!"
Yeah, the world doesn't quite work like that.
Apple does not dictate how people make purchases and how people spend their money. People will continue to use plastic and stores will continue to accept plastic for many many years.
NFC will slowly start coming into play, but it isn't even close to being a primary payment method at this point. While some major companies are on board, plenty more smaller companies and Mom and Pop stores won't.
Imagine, if you will, you're taking a vacation somewhere outside of a major city. You only have your iPhone with you and no plastic, because you don't want to do business anywhere you can't use your iPhone for purchases.
You run out of gas. The only gas station near you still accepts plastic.
You're going to feel mighty silly trying to pay for gas using your iPhone.