Others may disagree, but I think it may be because Parker's music is not about melody at all. As radical as his music is, Ayler was still playing melody - often abstract, atonal, non-tempered, intense melody, but still melody, with a familiar logic to the shape of his phrases. Parker's music is about sound and movement and intensity and space (not always all at the same time), but it's usually not about melody. He's working from a different aesthetic from many "free jazz" players.
Or maybe I don't know what I'm talking about. But that's how it strikes this Evan Parker/Albert Ayler/Charlie Parker/Sidney Bechet fan.