Bonham had them mic'd. When 3-ply shells are amplified, you hear the fullness of the resonating wood at work. Could you imagine a thick shelled violin, bass fiddle, or acoustic guitar?
Again, the the same principle to stringed instruments is applied...thin wood for complete resonance. The wood sound chambers on stringed instruments are even thinner than the 3 ply drums.
A drum is an acoustic instrument and therefore requires a sound chamber, the thinner the walls of that chamber are the the fuller the sound.
-kelly