Why take on a person who reads things closely, thinks about them carefully, values privacy, and has a sense of integrity?
There are a bunch of reasons. But the business one is that modern companies can't concentrate power at the top if they want to be successful in the long term. Innovation and adaptation don't happen because the SEVP of whatever has a brainstorm. They happen because people doing the work are intelligent, well informed, and care about the customers, their colleagues, and the company. If the most important characteristic in hiring is "agree instantly with all authority figures" that's a recipe for organizational rigidity and stagnation.
Some of the best hires I've made have been "difficult". Because some kinds of "difficult" are just taking values seriously.
One reason would be: Negotiating contract terms in good faith proves that it's not a contract of adhesion. By making the contract non-negotiable in this way, Google also risks its existing employment contracts being deemed unenforceable, having certain terms voided, or being read in the least favourable interpretation in court.
So it's in Google's interest to at least pretend to negotiate.