Earlier quoted context omitted.
The average Googler doesn't get to pick the OS that their workstation runs. It's going to be Linux. The typical work setup is a browser, some kind of editor and terminals - which is something that works well in Linux.
It depends on the team, and the individual. Generally, a Googler does actually get to pick their OS, it's part of the onboarding process that every Noogler goes through, and you're given 30 days from your start to swap around and test the other platforms (gLinux, macOS, gWindows, or Chrome OS).
I'll fully admit that my onboarding experience is quite out of date since I've been there for a decade. When I joined I didn't really have a choice for workstation since I only worked on server side stuff. Sounds like things have changed.