This is because music has evolved as a mutated copy of part of the human language acquisition instinct. The mood change caused by music is a mutated copy of the mood change that accompanies initial language acquisition, and it serves a different purpose.
The mood change that accompanies initial language acquisition helps to focus the infant's mind on language as a separate important thing that has its own (somewhat arbitrary) rules that need to be understood separately from everything else.
The mood change that accompanies music serves to intensify emotions that accompany daydreaming - this helps us to "better" daydream, in a manner that does not cause us to confuse daydreamed emotions with real emotions (because we are always consciously aware that the mood change is directly caused by listening to music).
(More details at http://whatismusic.info/.)
Recognizing the harmony underneath a line isn't something a casual listener is going to do, but is essential for a musician who is trying to communicate with other musicians in real-time.
My point is that none of that is essential to recognizing it as music and getting meaning from it.
Music 'theory' is somewhat akin to linguistics (or language subjects). It can help you dissect and understand how things work in an abstract sense, but when it comes to actually talking (or playing music), you're operating in a different mindset.
The people who rely on music theory are non-experts in the same way that the people who rely on language class to speak are non-native speakers.