They had a push back in 2006 remember? They had a lot of discounts on fee and were fee free in many cases for some time. Large retailers like Buy.com and Newegg had them too. I see some other checkout history in my transaction history with CellHut and Dick's sporting goods. It looks like I also bought my first Android Phone via Negri Electronics using Checkout as well.
I'm not suggesting that it's popular. It's one of those things Google tried that didn't really take off, but my point was that they had the back end payment processing capabilities already. The system was setup, and so just like you can pay a restaurant through the PayPal app, it could've been just as easy to set them up through Google Wallet. It's not so much that PayPal went and got all the vendors registered through PayPal, but I think they worked with partners like Eat24, Grubhub, Seamless, etc to get an ordering and payment system to work.
My main argument is that NFC payments only goes so far, and if Google can't get people to change the way they pay at the terminal, I don't see why they couldn't have offered a multi prong approach given that Wallet is also meant for sending money between individuals.
I think in the end you get a product that's specialized in NFC but offers no real advantages. In terms of sending money between people, there are alternatives that are far more popular and have wider adoption, and given that there's no ability to just pay a vendor through the app itself, internet payments (be it mobile or non mobile) will never take off either. So really, what is there left for Google Wallet?