Google's actions in this area speak for themselves. Even in the few instances where they have been involved in patent infringement cases on the "offensive" side, the suits have been quite obviously defensive in nature (eg. the suit vs British Telecom).

The nature of reality as it applies to patent law is why I don't fault companies for acquiring lots of patents, but do fault them when they use those patents offensively. Google remains among the very few large tech companies I respect when it comes to patent actions.

The fact that they're not on the offense is not really meaningful. Most of the value of property and contractual rights is prospective. I bet Google has never sued someone for planting a farm on their campus lawn--that doesn't mean they're indifferent to the existence of that property right.

Google acquires a lot of companies for their IP. Not so they can sue people for infringing on it, but so they can use it. The property rights create a legal structure that allows those kinds of transactions to happen. Like with any other property right, that's the value of a patent--giving people a "thing" in which they can transact, which they can book as an asset, etc. Ideally, a lawsuit only happens when things go sideways.