Why are Revisions B and C still posted ?

Hi all,

 I think several people have asked this question before and
 I dont recall if we ever came up with an answer...

 I just noticed that PIDX (see

 http://committees.api.org/business/pidx/businessmessagessubcommittee.html )
 is working a current project using Revision C.
 Should we ask them to use the base, approved spec instead ?

 Thanks,
mike dillon