> Why has nobody come along and created an alternative standard library yet?
Probably, IMO, because not enough people would agree on any particular secondary standard such that one would gain enough attention and traction¹ to be remotely considered standard. Everyone who already has they own alternatives (or just wrappers around the current stdlib) will most likely keep using them unless by happenstance the new secondary standard agrees (by definition, a standard needs to be at least somewhat opinionated) closely with their local work.
Also, maintaining a standard, and a public implementation of it, could be a faffy and thankless task. I certainly wouldn't volunteer for that!
[Though I am also an outsider on the matter, so my thoughts/opinions don't have any particular significance and in insider might come along and tell us that I'm barking up the wrong tree]
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[1] This sort of thing can happen, but is rare. jquery became an unofficial standard for DOM manipulation and related matters for quite a long time, to give one example - but the gulf between the standard standard (and its bad common implementations) at the time and what libraries like jquery offered was much larger than the benefits a secondary C stidlib standard might give.
Probably, IMO, because not enough people would agree on any particular secondary standard such that one would gain enough attention and traction¹ to be remotely considered standard. Everyone who already has they own alternatives (or just wrappers around the current stdlib) will most likely keep using them unless by happenstance the new secondary standard agrees (by definition, a standard needs to be at least somewhat opinionated) closely with their local work.
Also, maintaining a standard, and a public implementation of it, could be a faffy and thankless task. I certainly wouldn't volunteer for that!
[Though I am also an outsider on the matter, so my thoughts/opinions don't have any particular significance and in insider might come along and tell us that I'm barking up the wrong tree]
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[1] This sort of thing can happen, but is rare. jquery became an unofficial standard for DOM manipulation and related matters for quite a long time, to give one example - but the gulf between the standard standard (and its bad common implementations) at the time and what libraries like jquery offered was much larger than the benefits a secondary C stidlib standard might give.