the ash-heap of history is littered by companies and organizations that have decided that everyone else was wrong, and they knew better and could design such a great system that everyone else would abandon what they use to jump on board.
You act as if the POSIX (and Single Unix Specification) standard is something handed down from on high that hasn't changed in 20 years.
The last revision to POSIX and SUS took place within the last couple of years, and the next one will take place within the next few years.
These standards work by looking at the things that people are developing, and getting consensus between the different developers as to what they can agree on, They then have those developers go and implement what they are proposing, and it only gets into the standard after there are running implementations.
by definition this means that they encourage new, non-standard, things to be developed and deployed (they can't add something to the standard if it hasn't been deployed yet)
The problem isn't with the idea of enhancing things, it's with the idea that standards don't matter, nobody else matters, only develop for yourself and to #$% with everyone else.