We need sane font rendering in browsers that treat things like alignment in a way that we’d expect for the 99% case. If I say “center” it should just fucking center.
And if you're really targeting people that have trouble loading such a font file, then you have much, much bigger problems than centering things (you basically cannot put any image on your website).
Where's that ratio coming from? Shipping fonts is just good practice when you want your website to look consistently on all platform, it doesn't mean anything else about how the website is made.
Also, 100kbps is a very slow connection, it's 2 orders of magnitude less than the 10Mbps you talked about earlier, and when you have this kind of very poor connection everything is kind of slow anyway (even the very barebone HN's front page is 120kb!).
Why would it looks bad elsewhere?
> All websites should use the system font for body text.
Wait what? There are very different requirements when it comes to reading system widgets and actual text! (like we don't use the same kind font for code and prose).
Now disabling custom fonts altogether makes sense of you are trying yo save bandwidth, but then you aren't mad if things don't properly align.