Here you go guys, I found the interview on-line where I said Jerry mentions Bob not being too happy with it.
It has two interviews, it's in the bottom one which is about acoustic playing:
http://members.tripod.com/malfalfa1/garciainterview.htm
To quote the interview and Jerry:
Guitar.com: Why has the Grateful dead limited its acoustic sets?
Garcia: I don?t know. I think [Bob] Weir doesn?t feel comfortable playing acoustic music. I personally would like to do it more often. Bob doesn?t seem to like to do it very much, so we don?t press it. If anybody feels even a little negative about something, we don?t do it.