The new Nexus 7 does not support Google Wallet - officially. Why? It lacks the hardware component necessary to securely store your payment credentials for NFC transactions, aka the "secure element." The AT&T and Google Play Edition HTC Ones don't have this element, either.
The latter, to me, is something I can understand finding a bit annoying. The former, though - that being the new Nexus 7 - really isn't.