Their FAQ says that they don't (currently) use cookies, but it also includes the sentence "Google Fonts logs records of the CSS and the font file requests, and access to this data is kept secure", so they could still do some IP-based analytics.
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.