Hi Scott,
I can think of a couple of reasons!

The pre-registration packets contain goodies. Suppose I wanted the goodies, but knew I couldn't attend. I could "pre-register" to get the packet, then "back out" at the last minute.....thus messing up all anticipated attendance figures, etc.

There's about 800 people pre-registered. Betcha if "absentee" pre-registration packets were issued, the membership numbers would go up, and a LOT more folks would pre-register! After all, we ARE a collectors club!! Our mission is to COLLECT!! Mike could register "Coco M. Poole" as an associate member and get more goodies! If there were 1800 pre-registration packets, instead of 800, would the contributors be as willing to supply goodies?
Just my opinion.....