The standards effort that began with a 20-page specification in 1980 has grown to a 600 page extravaganza of technical information. The justification is much more simple - you have to stop sometime and get a standard printed. Popular interfaces never stop evolving, adapting, and expanding to meet more uses than originally envisaged. Interfaces even live far beyond their technological lifespan. This will probably continue for another year or so before the high point is reached, and it will at least a decade before SMD is considered to be insignificant.
Impatience is as good an answer as any.
The SCSI-3 effort is actively under way right now, and the workload of the committee seems to be no less than it was a year ago. What is pleasant, is that the political pressures have eased. There is a major difference between the standards for SCSI in 1986 and SCSI- 2 in 1990.