Actually, the semitones aren't spaced evenly here. The white notes on a piano keyboard are spaced evenly, and then the black notes are half-way between the white ones. So it's rather like conventional notation in that respect (the notes of the diatonic scale are equally spaced, as long as you're in the right key) but since it doesn't have a notion of key signature you can't arrange for that to remain true in (say) F minor.

This preference for some keys over others is pretty much built into the piano keyboard too, and the notation is specifically intended for keyboard music, so it's not obviously crazy. But it certainly doesn't have the property that the semitones are equally spaced.