Why do the authors of the C/C99 standard, don't specify a ..standard for the sizeof floating point types?

Programmer Question

This is considerably puzzling since planes had gone down due to overflows.

I noticed on windows and linux x86, float is 4bytes, double is 8, but long double is 12 and 16 on x86 and x86_64 respectively. Why aren't they same? Why do they try to achieve? It can't be merely tradition since C99 is supposed to be breaking such barriers with the specific integral sizes. Or at least I hope it's not merely tradition or incompetence.

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