NFC is used for a bunch of things e.g. credit cards, transit passes, inventory control tags, etc. You'll find it's pretty much all around you, even if you never see a sign for Google Wallet. You'll never see a sign for "NFC".
Mobil Gas Speedpass, Caltrain/BART Clipper transit cards, etc. are all NFC-enabled technologies. Most checkout counters where I am (NYC) are all NFC-enabled so you can tap to pay with your Chase, Citi, Amex, etc. card which all have NFC tags embedded in them.
Google Wallet is really just 2 things -- a refillable debit card, and a proxy to your Citi card if you have one. And whoever wants to write these proxies to physical cards.