@Tricky:
How much overhead we talkin', here? Figuring out which values to put next to each other isn't free. :-)
HAM was clever for saving memory, but really didn't have any other advantages. Even in its heyday, HAM was useless except for static pictures and letting Commodore advertise the Amiga as a 4,096 color system. It was even more uselss on AGA due to the rediculous speed of the new blitter (the same as OCS, basicly).