Part of the reason is likely related to density of material. We went with Roxul Safe and Sound for our basement and the sound dampening is phenomenal. We did all the interior walls during the basement reno, not just the media room. The increased thermal insulation is also incredibly noticeable. The basement stays warm in the winter and cool in the summer with a slightly too cool condition in early spring as the furnace doesn't turn on as much to circulate the air.
"Those who preach the myths of audio are ignorant of truth."