D&D 3.5e and Pathfinder are somewhat-special among the systems we run into in that their mechanics are spread across many texts, as opposed to being defined in one place. Of course, SRDs help with this, but are somewhat-necessarily limited in what they cover; people who are new to 3.5e and/or Pathfinder, though, may not appreciate this all that well.
Practically speaking, this means that "read the book to me" turns into "read which book to me, again?" as the answer may not be in the PHB or even the SRD, but in some splatbook a novice player may never have heard of...so what should we do with questions where the answer at first appears to be simply "read the PHB/SRD/DMG" but, upon a second look, isn't?