Do you think Google is reading the contents of drive documents? I struggle to make the connection between those kinds of business apps and advertising.

Perhaps they get some usage data of how/when people work?

I do believe much of what Google does (i.e. chrome) is to benefit their ads business, but I think it's a bit cynical to think that's true of every product they have.

FWIW I've worked at companies that use both Microsoft + Google suites (mostly drive + calendar + mail) and generally preferred Google's. I did not have any issues like the post mentions.