I think it is more psychological. The song (if it is a lyrical piece) registers with you about some current issue. Therefore it stays in your head because of it's psychological impact. A psychologiacal resonance I guess. Melodically I think you may be right jeenia but lyrically I think it may relate to a particular mood or an issue that the person may be having at the time. Alot of times your choice of songs reveals your mind set at the moment not the other way around.