OK I’ve been thinking about this for quite awhile now: Why does the Pentatonic minor scale or blues scale (which is also a minor scale) sound so good over certain Major chord progressions (e.g. I, IV, V)?

My thoughts on this are that the Pentatonic minor and Blues scale although they both have a flattened 3rd (which makes them minor scales) they do not have a 2nd note. This I think makes them more ambiguous sounding compared to the Natural minor scale, for example, which does have a 2nd note which emphasises the minor nature of the scale.

Anyone else have any theories why these two minor scales sound good over some Major chords?