Although I do wish there are a few standard font that is shipped across all browser. Sometimes I want the website to appear exactly the same on all System.
See my comment to the parent for an example of a site that needs to look the same (or rather - a portion of site - an HTML Canvas) that has to look the same on every device and which needs a specific font loaded to work properly. For my case, having a font that was guaranteed the same in every browser would have been very nice, and I would have gladly used that if it worked and fit the theme closely enough.
Even if there was consistency in the actual fonts their rendering depends on the platform/engine or even just the device settings. If you want precise display metrics you should use an image (SVG counts). If I've got large text enabled on my phone we could have the same exact device and my display metrics won't match yours.
Nice, but it's more important for my browser not to leak information about me via what fonts I needed to download.
Also, it gets really annoying when sites demand that my desktop look like my mobile phone but blown up really big. Twitter's already that way, and the Facebook redesign did the same thing.
There are a few metric compatible fonts used by stuff like pdf. and so on. I believe an alias for these fonts are needed. Obviously add an emoji and UI font. that will be the best
And with smartphones, they're no longer installed on every system. I really wish that Chrome and probably other browsers would install a set of fonts from Google Fonts. I don't see a reason why this shouldn't be possible. That's what most sites use, anyway. I guess it's related to Google being able to track usage of these fonts.
For a page that really needs to look "exactly the same" everywhere it's viewed, maybe PDF is a better choice than HTML+CSS.