Because I would bet that the security professionals working for and contracted by Google and Facebook to be an order of magnitude better at their jobs than those hired by Nokia. I would expect Google and Facebook to be better at closing holes and better at detecting and closing security breaches if and when they do happen.

Because this would only get the information for people who happen to be browsing to those services through specific Nokia phones.

Facebook and Gmail don't handle your connection to your bank.

Apart from that, we already know the Chinese have hacked GMail accounts on several occasions, so Google is already a definite target and the Incidents that have been reported may be just the tip of the iceberg so far as we know.

We also know that there have been cases of corporate and government espionage in the recent past. This is happening, right now, and we may never know how extensive it is. It's entirely possible that Nokia could become a target of either technical or even employee infiltration. If so, covert access to a service like this would be a fantastic coup, especially since Nokia phones are still popular in many parts of the world with unscrupulous and technicaly sophisticated governments.

Of course it is. But that's beside the point. The fewer servers that I interact with that have giant targets and potential security holes the better.

You'd be surprised what sensitive details people send via Facebook messages, email and other insecure communication tools.