Maybe the implication is rather that a simple melody is something we can all understand and enjoy, while complex, challenging music is enjoyed by only some people (members of this list, and the like)... in other words simplicity is kind of the 'common denominator' between all (or most) people.
I saw the noble laureate Roald Hoffman speak on a variety of topics from chemistry (his main field) to poetry (he's also published poet) to philosophy and psychology. One statement he made that didn't sit well with me was regarding the innate human desire for simplicity. He contended that humans aesthetically desire, seek out, and try to create simplicity in all things. That simplicity is an overarching principal of organization in our cognitive system, thus our perception. He used a simple melody or a simple molecule as examples of things that, he claims, resonate with all people favorably. That confused me, as I often look for complexity and challenges--particularly in artistic, aesthetic concerns. So my question to everyone is: Do some people actually buck this trend, which I do see in a great many people, or is there actually some underlying need for simplicity at work for those that seek complex or chaotic aesthetics.