Yep, like everything, it's a trade off. In return you get a very robust platform and free fonts.
(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.)
Would you condemn web typography to the use of "web safe fonts" forever?
Why not let everybody have websites look how they want them to look? I'm kinda sad this vision gets so little attention, that instead we all try to push our vision on our visitors. Even if the web turns app platform.. just like we have configurable desktop managers, browser could still let everybody customize how websites look - if only websites could stop with the "story telling" and "experiences", and concentrated on utility and information. We're too addicted too shiny for our own good already.