If you take the circle of fifths, there is only one scale (of each major and minor) where the whole scale has an enharmonic equivant, that is f# major = G flat major (and D#minor = e flat minor). This is the scale at the polar opposite from C major/a minor, at 6 o'clock on the circle.

Both scales are practically never used.

So, in practice, people tend to use 1-4 # and 1-3 flats, i.e. the upper half of the circle of fifths.

Most instruments have "preferred" scales, like E for the guitar (because the strings are E A D G B E), G or D for the violin (strings are G D A E), and some brass instruments tend to favor keys with flats, like B flat or E flat.

Chopin liked to use a lots of accidents (= black keys?) in his piano pieces, maybe a pianist can explain why. But that's not the majority trend, in general.

Maybe you will also find some songs in keys you find in the lower half of the circle of fifths. This might be for the singer's comfort. Maybe the song was to high and then it was transposed to a semitone lower, and that's how it found itself in the lower half of the circle.

What you propose - abolish the lower half of the circle of fifths would not really be practical. For one because in this case you would not have a scale for every different semitone that exists. And also: for the sake of consistency within a scale, within a piece, it is preferable to call a not a# in some contexts and b flat in others. It would not be easier to read b flat in a context of E major or so...