Any thoughts on why Google is doing this other than a perverse will to take over the entire Internet?
My thought is that they're hoping this will encourage more text instead of images as text. That helps them index more information and collect more data on the whole web.
Microsoft (and Apple) did a similar thing back in 1996–7 with "core fonts for the web" in which they tried to push a standard pack of fonts out to everyone so that web designers could assume that end users would have certain key fonts.
My thought is that they're hoping this will encourage more text instead of images as text. That helps them index more information and collect more data on the whole web.