As far as the unsavory interpretation of how they could conceivably use Fonts data to further that end: calls to download their fonts are another touchpoint with the Google ecosystem, and a theoretical vector for further tracking the browsing behavior and device graph of an individual.
That said, traditional font licensing for commercial use is absolutely bonkers[1][2][3]. Even if Google is using the data they collect from serving font files to feed into their user tracking, they've done a service to the web[4].
[1] https://designshack.net/articles/typography/what-is-a-font-l...
[2] Working at a creative agency, I learned that we can't so much as legally use a client-dictated (and licensed) font in a mockup without paying thousands of dollars for a license ourselves.
[3] Webfonts tend to be licensed on a per-pageview basis. One client got hit with a temporary flood of scraping/bot traffic, and the biggest economic impact was the unexpected six-figure font bill that month. We convinced them to put the site behind Cloudflare and used a Worker to strip out the font include for suspected bot traffic and inadvertently lowered their licensing cost by more than our annual retainer.
[4] I can't say how it is everywhere, but working at one of the top three marketing agencies, Google Fonts are the only approved open-source fonts we're allowed to use (since they're primarily free for commercial use, as well). Not every client is able or willing to absorb a 5-6 figure font line item for every engagement, so without Google Fonts we'd (and I presume other major agencies) would be stuck with using system default fonts everywhere.
More importantly though, it gives Google accurate insight into web traffic (many users block Google Analytics, but almost everyone loads web fonts), and it allows them to crawl websites more easily – before web fonts, many websites used pre-rendered PNGs to show web-unsafe fonts, which made crawling impossible.
Google has poured a lot of money into this, the fonts are free and open source, and the users aren't the product. Overall, I think it's a rare win-win story in this age of dystopian adtech.
Why, though? Not charity, I'd assume. The only other answers I can come up with are pretty damn nefarious.
> it allows them to crawl websites more easily – before web fonts, many websites used pre-rendered PNGs to show web-unsafe fonts, which made crawling impossible
1. A lot of text was rendered into PNGs, and that made the web less searchable, as well as less accessible, slower to load, and less mobile-friendly. All 4 of these factors do have economic impact at Google scale.
2. Fonts were one of the few features that Flash had that HTML5 was lacking, and we wanted to accelerate that transition. Again, mobile was one of the major driving factors.
3. For a while, we were organizationally funded under Google Docs. Again, fonts were one of the major missing features compared with Microsoft Office, so filling that gap was strategic. Here, our open source approach really paid off, otherwise dealing with proprietary font licensing in the context of documents that can be shared and copied would have been nightmarish.
4. To the extent that you are able to make the case that fonts make ads better (or advertisers happier), getting modest amounts of funding ceases to be a problem. To be clear, when I was on the team this was more of a glimmer of future abundant resources than day-to-day reality.
Lastly, while "charity" isn't exactly the right word, the motivations of the people working on the team are/were basically that we love fonts and want to make the Internet better. At Google scale, we were able to sell the project using basically a combination of the above arguments.
Never once when I was on the team were we asked to implement any form of individual user tracking, nor did I hear a suggestion of such a thing. All our work on collecting analytics was to improve performance and quantify our impact. I have no reason to believe things have changed on that front since I was directly involved.
I loved that site.