It a normal thing in an evolving world: Some things are invented, documented and even standardized but because of one reason or the other they never see the light of day. GSM, UMTS and LTE, all of them part of the 3GPP standardization process, are no different. Today, there are many many features and options described in the specification documents that have never made it into real networks. Documents are bloated and when you are looking for something specific they are in the way of finding what you want. So how about having one 3GPP release dedicated to just one purpose: Clean up the specs and remove stuff that is irrelevant today!?
It's not that this never happens, take for example this GERAN report from 2009 in which it is noted that T-GSM 900 and PBCCH stuff was removed. Nevertheless I think the specifications would benefit from a somewhat larger effort. I guess it is unlikely to happen, though, because where's the immediate financial gain of cleaning up…
i don’t think it’s gonna happen either. not for financial reasons though, but it would require enormous effort to do that, almost a mission impossible.