I've learned a lot from all the comments and have come to the conclusion that the usage is circumstantial, i.e., depends on the attendant conditions. This morning I heard a dignified-sounding talker on the radio say, "It depends on where you're at." This construction always rankles me in the same way as does "the reason why" or, more so, Anonymous's "what it is is..." Now, however, I am swayed by John's quotations from classical writers and have decided that the "why" is indeed an emphatic in some situations and is detritus in most other situations.