Uneven scale intervals make free transposition impossible

Evidence

The pentatonic scale has other problems, though, not the least of which are too few notes for modern music, and the inequivalence of the notes that do exist. Because the intervals are uneven, from one note to the next, it is not possible to transpose music up or down freely, except by whole octaves. This means that a song composed beginning on the tonic of 100 Hz could simply not be played transposed up to a tonic of 150 Hz. The required notes would not exist, and the substitutions would sound awful. — Eric J. Heller, Why You Hear What You Hear- An…, 2383