Maybe I'm dumb, why wouldn't they be saving money by not paying for Office? Obviously they could buy it for every employee, including the majority that don't need it, but why? They could also just light money on fire (but why?)?
I work for another FAANG and we don’t use MS Word. It certainly isn’t “standard” for us. It’s not standard for two of the three FAANG companies, so “everywhere” is inaccurate. Being popular isn’t the same thing as standard. Pages is a far more usable for the vast majority of use cases. Most people aren’t creating extremely complicated word processing documents in their day-to-day. Word is a bloated mess. Keynote is far easier and more elegant than PowerPoint. Excel however certainly shines for big spreadsheet work, but for most spreadsheet work Numbers and the google spreadsheet are perfectly fine.