ZOPFLI compression not the default?

[hashimaziz1]

Is there a particular reason the ZOPFLI compression is not default and has to be explicitly used with --zopfli? I'm guessing zlib compression is being used instead, which is generally agreed to be inferior to ZOPFLI, so if the ZOPFLI option is there and doesn't involve any major downsides I'm confused as to why it hasn't been made default and --zlib added as an option instead (although it wouldn't even be necessary to include zlib compression at all, if desired).

I currently use sfnt2woff for this very purpose, and also recommend it here for WOFF conversion, but if webify enabled Zopfli by default I would no longer see a reason not to switch over, because webify is so much easier to type.