Also, if I remember correctly, by mid-1997 there were hopes in the family that Carl might recover, and these hopes vanished by the end of the year (please correct!), so maybe the group, or Mike, or Carl himself thought that he could work better at recovery if not touring.
Ironically, at Audree's funeral a lot of folk thought Carl looked pretty good (considering) and were hoping for the best... then, after Brian watched the 1998 Super Bowl with him (I think at Jerry Schilling's place), he reportedly told Melinda on the way back "I don't think we're gonna see him again". That was on January 25th. Carl died 12 days later.