From: Sime Surgeon, Ch 9. '...When Digen and Ilyana arrived, a vigil party was in full swing, the room filled with channels, but no Gens. The objective of the vigil party was to bridge the time of depression just prior to transfer without aggravating need...'
(Source: Index card file. Sime Surgeon http://www.simegen.com/sgfandom/rimonslibrary/surgeon/SURGEON1.html) To bridge the time of depression just before transfer without aggravating Need, hence, attended only by channels keeping their show fields low. Only held for channels --- they're the only ones who are allowed to go so long into Need that they feel it in the extreme.