Before ~ 2007, Google didn't believe in project managers. There were actually no project managers roles (even though some people were probably doing considerable amounts of project management) and the expectation was that engineers would know enough to structure efforts and timelines.

That evolved into a situation where program managers (mostly - programs have a sense of scale right??) exist in most orgs and are critical to keep things aligned. There were (are still?) even internal conferences just for program managers.