Using sprites instead of fonts to support users with foreign fonts disabled means degrading the product for some other users. Building a polyfill means not spending the time improving something else.

Why do you consider "support everyone" to be obviously better than "build a better product for a subset of users"?

I feel like the undending debates around this issue (most often regarding JS) exist because some people on HN look at it through a business angle where #2 can make complete sense, while some others look at it through a Web ideals angle where anything but #1 is heresy.

Edit: To be fair, the Web ideals remark doesn't seem to apply to you. You rather seem to consider than being pretty is way less important than supporting more people. But why? Being pretty has been increasingly important this past decade, and especially so regarding blogs where being pretty is one of the few differentiators.