Contrary to popular belief, music doesn't "use" theoretical constructs such as the diatonic scale; listeners use them to interpret music.

In other words, the important fact about the diatonic scale is not whether it is presented explicitly in music, but that even when it isn't, it is still the basis for a listener's comprehension of the pitch structure.

(Also note that the pentatonic scale is a strict subset of the diatonic scale.)