EBCDIC based IBM mainframe SYSADMINs on BITNET were particularly notorious for being pig-headed and inconsiderate about communicating with the rest of the world, and thought they knew better about the characters their users wanted to use, and that the rest of the world should go fuck themselves, and scoffed at all the unruly kids using ASCII and lower case and new fangled punctuation, who were always trying to share line printer pornography and source code listings through their mainframes.
"HARRUMPH!!! IF I AND O ARE GOOD ENOUGH FOR DIGITS ON MY ELECTRIC TYPEWRITER, THEN THEY'RE GOOD ENOUGH FOR EMAIL! NOW GET OFF MY LAWN!!!" (shaking fist in air while yelling at cloud)
It was especially a problems for source code. That was one of the reasons for "trigraphs".
>Trigraphs were proposed for deprecation in C++0x, which was released as C++11. This was opposed by IBM, speaking on behalf of itself and other users of C++, and as a result trigraphs were retained in C++0x. Trigraphs were then proposed again for removal (not only deprecation) in C++17. This passed a committee vote, and trigraphs (but not the additional tokens) are removed from C++17 despite the opposition from IBM. Existing code that uses trigraphs can be supported by translating from the source files (parsing trigraphs) to the basic source character set that does not include trigraphs.