It's important to note that most engineers at Google don't actually work on Ads or anything to do with monetization directly. Most will be working on things like Search, Gmail, Android, Maps, Docs/Drive, YouTube, Chrome, etc etc.

I'm pretty sure Google doesn't really have a plan to monetize any of those things (other than ads), but I think it's also pretty cool that a small minority of the company makes enough money to let the rest do pretty much whatever.