I thought so too first but then I read Trevor Perrin's response to Lars Eggert: http://www.ietf.org/mail-archive/web/cfrg/current/msg03778.h... and it seems quite clear that Eggert failed to consider a number of important aspects, just one example from Perrin's mail:

> So unlike the title "co-chair" might imply, and unlike in many other organizations, IRTF co-chairs are little more than group secretaries.

The chair is far more than a "group secretary". As RFC 2014 section 5.3 states:

""" The Research Group Chair is concerned with making forward progress in the areas under investigation, and has wide discretion in the conduct of Research Group business. [...] The Chair has ultimate responsibility for ensuring that a Research Group achieves forward progress. """