[jandrese]

It's all they needed. 6 bytes per address, and 2 more bytes to mark the protocol. Back in the 70s and 80s memory was very expensive and developers bent over backwards to save bytes everywhere. This is also why IP addresses are only 32 bits long, even though they knew that it wouldn't be enough if the protocol went global.

Hindsight is 20/20, and a lot of times people don't appreciate the constraints these old systems had. This was being developed decade before the Commodore 64 came out with its luxurious 64 kilobytes of memory (39k usable).