Earlier quoted context omitted.
In return for what? Google's not profiting off of Google Fonts, because I'm sure that whatever data they get from it could be collected by their other services.
Logged visits to sites they would otherwise not get. Font request+referrer is useful information.
(I'm not making any comment on Google's general strategy or how many people would actually understand that they might wish to protect their privacy in this way, just pointing out that it can be done.)