I think some LISTSERV options are set by list-owners according
to their desired style of interaction with automated and manual
processes, in part based on their interest, available time,
expertise, and list experiences.  Auto-delete is one such
option. SUBSCRIPTION=OPEN,CONFIRM is yet another.
 
There is no "right" answer, just pros and cons -- one owner's
pro is another owner's con.
 
/Pete Weiss