I don't know about that, mightn't inefficient datacenters cost more per query, leading to worse servers, leading to higher latency, which users care about?
Yes, users care about latency, but less efficiency doesn't necessarily lead to higher latency. (I have no idea what "worse servers" means.)
As long as Google can afford to provide decent anwers with acceptable latency, it will have users.
I think that efficiency is like programming effort, algorithms, and programming languages in that users don't care. They only care about results and the costs that affect them.
Google's users don't care how efficiently it runs its datacenters.