驾崩 was reserved for emperors and empresses. Lower ranks used 薨 (hōng) for nobles, 卒 (zú) for officials, and 死 (sǐ) for commoners - death vocabulary mirrored social rank.
memory
驾 = imperial carriage (the emperor's 'ride'), 崩 = to collapse. Picture the imperial chariot collapsing - the ruler is gone.
