I understand (after reading the entire discussion up to this point) the hardware 'limitation' that prevents the full implementation of the "AirDrop" product. It is clear to me however that this thread has long since evolved from the specifics included in the OP's question (i.e. the OP's question was asked and ANSWERED). If I were to take the liberty of summarizing the common theme(s) presented here: an 'Air Drop Lite' feature would be very desirable!! The hypothetical 'lite' version would offer the ability to transfer the same files that the full-blown AirDrop is able to, but at a limited rate of transfer that is determined by the hardware of the devices involved in the transferring of the files. I think that it is great that there are 3rd-party apps that can do this with a select number of file types (e.g. photos), but I, and many others, prefer the in-house approach; one main reason for this for me is the seamless integration with iOS and there are no ads taking up precious screen real estate urging you to upgrade, etc. I should note that these are not the only reasons that I prefer an in-house method of wireless file transfers.
One specific scenario in which I could have benefited from this feature was a .pdf file transfer from my iPhone 5 to my iPad 3 (or more precisely, iPad 3rd-generation) so that I could read the document on a larger screen. It would have been nice to just slide my finger and turn on the Bluetooth and accomplish this using the identical method on both devices (not fancy/3rd-party app workarounds) with the Airdrop feature!
I have to admit that I personally have not had enough experience with the AirDrop feature, but I have noticed through this discussion that WiFi is needed in addition to Bluetooth to accomplish this? Maybe my complaint lies with the feature as a whole then. Having the option to wirelessly transfer files in fast and secure(?) method through AirDrop as it stands now is great, but my preference would be to have an alternate option that spans more devices (possibly even non-Apple) and can transfer the file wirelessly without Wifi (i.e. Bluetooth only)! I do not know the specific technical requirements of doing this wih a variety of file types, but I remember children's toy devices from over 15 years ago that could send the equivalent of a text message (it possibly did in fact use SMS---I am not sure).
All that said, I agree with others that a simple explanation would more than suffice as to why this widely-requested feature is not offered. If one were to be provided by Apple, I, and many others, would quit 'whining' and move on!!