Comment by Macha

If you hand UTF-8 that actually uses anything added by utf-8 to something that can only render ASCII, the text will be garbled. People can read garbled text ok if it’s a few missing accented characters in a western language, but it’s no good for Japanese or Arabic.

In networking terms, this is like a protocol which can reach ipv4 hosts only but loses packets to the ipv4+ hosts randomly depending on what it passes through. Who would adopt a networking technology that fails randomly?