> An explanation I heard ~10 years prior is that doing so exposed bugs in CRT and nobody wanted to fix them.
What I've heard is that the issue is not with the CRT, but with applications using fixed-size byte buffers. IIRC, converting from UTF-16 to any of the traditional Windows code pages requires at most two bytes for each UTF-16 code unit, while the UTF-8 "code page" can need three bytes. That would lead to buffer overflows in these legacy applications if the "ANSI" code page was changed to UTF-8.
What I've heard is that the issue is not with the CRT, but with applications using fixed-size byte buffers. IIRC, converting from UTF-16 to any of the traditional Windows code pages requires at most two bytes for each UTF-16 code unit, while the UTF-8 "code page" can need three bytes. That would lead to buffer overflows in these legacy applications if the "ANSI" code page was changed to UTF-8.