> AFAICT, there is no good use case for showing floats in in hex

It is my impression that hexadecimal is more common than binary, in the
numerical analysis community, for exact representation of floats.

For example:
http://hal.archives-ouvertes.fr/docs/00/28/14/29/PDF/floating-point-article.pdf

"Hexadecimal floating-point representations are especially important
when values must be represented exactly, for reproducible results — for
instance, for testing “borderline cases” in algorithms."

Or course, without hex float literals or an equivalent function for
input, hex float output is not much use.