Can I share a secret with you?
Smartphones really aren't that smart.
They do a small amount of thinking for themselves, but they depend quite a bit on the information you give them about yourself. Yes, they're like IBM's Watson -- or pretty much every Valentine's blind date you've ever had.
Siri has had her troubles understanding you -- both your voice and the strange way you sometimes think. Even Apple co-founder Steve Wozniak has called her something of a disaster.
Google has Google Now -- which is very now and very Google.
The more information you give it about yourself, the more useful its offerings are.
Why would you be bothered about old-fashioned idiocies like privacy (or 4G LTE) when your Nexus 4 can help you not be late for something important or find the French word for "vegetable" while you're in Paris, staring at a sea urchin?
More Technically Incorrect
After Samsung, Google is the one brand that has used advertising very effectively to create a distinct (and much needed) emotional connection with an audience that might otherwise be suspicious.
This ad manages to marry the warm with the useful, the local with the worldly. It doesn't bother showing a voice capability to directly jab at Siri, because it has something potentially more interesting to offer.
The idea that you can be given the right information at the right time is extremely powerful, when we seem to spend most of our lives being given the wrong information by people (and machines) who really couldn't care one way or another.
Of course, Google has managed not to be able to give people the right phone at the right time, by somehow failing to ensure that enough Nexus 4s are available for humans to do quaint things with them -- like taking them home, for example.
Still, imagine if you could find this phone at your local Best Buy by just casually wandering down the street. Yes, now.
That would be a revolution, wouldn't it?