Lack of low end, most usually by means of some kind of significant roll-off leads to a psychoacoustic presentation which, inevitiably, is more treble biased (unless the treble is also rolled off). High amounts of treble energy is readily percived as a quality of higher detail level articulation or as a more rapid transient response rate. While these qualities are not incompatible with or antirequisate to a presentation that is bass-light, one does not in inherantly beget another. Realism is detail, detail is realism, real life doesn't go "wham wham wham" in the bass. Thus rolled off bass is realistic to those same ears.