Sorry, gotta disagree with gonk. The main reason is isolation. No speaker should be on a flat surface, be it a shelf, speaker stand, or floor. Vibrations and coupling between the speaker and whatever it's on need to be minimized. My speakers (Hales Transcendence 5) would be solid on the floor, but they are on cinder block and then tiptoes. The difference, especially in the bass, is night and day.