Because the difference between a $10,000 AVID and a $50,000 AVID of the same period is just software options which are enabled by the dongle keys (same hardware cards pretty much with maybe the exception of the Audio card). Early systems didnt have a dongle, they had a KEY on disk that meant if your card died you were SOL until avid provided you with a new key disk for it.
AVID didn't realy make their own cards either, they modified others designs as needed. For example they used a Targa 2000 Nubus card in one of their systems that they modified the input section of the board along with making a plug that would connect to their DSP board (also changed the card BIOS). Early AVID systems just used slightly modified Nuvista boards and Audiomedia I/II cards and commodity SCSI cards.