It's basically Y2K without the sense of urgency. People assumed ASCII, or at least single-byte supersets of ASCII, would pretty much be the norm, so they never

It's basically Y2K without the sense of urgency. People assumed ASCII, or at least single-byte supersets of ASCII, would pretty much be the norm, so they never bothered with anything else. And since there are no apocalypse nutters breathing down people's necks to fix it, it often gets deprioritized. Plan 9 actually tried to do something about this: it assumed Unicode for everything, and invented their own encoding for the process. The OS didn't work out so well (regrettably), but we still use their encoding: it's called UTF-8 now. Still a superset of ASCII, I guess, but at least we've gotten beyond the single-byte assumption.