Technically, that's a "how" not a "why" ... I, too, am curious as to why some people feel the need to not follow the conventions of the language that they use in things like their name, so I'd love to hear brian_d_foy's reason. (I've googled a bit, but haven't found one beyond "it's my preference" - which isn't a reason, either, IMO - at least not a justification I can wrap my head around.)
As an example, I once worked with a guy who went by the name "Tarver" - a nickname he adopted when he was younger, largely because, as a Polish person living in Canada, with a very, very Polish name (both given and family) that no one here could pronounce, he actually was trying to do the rest of us Canucks a favour by using a name we could handle. Then, to allow him to actually legally use the name, he went and legally changed his name such that it was now his surname (note: I didn't use "family" as the label for this name). Then, upon gaining employment with our company, we had a few difficulties getting everything set up to solely use his surname (legally, one can go by just a single name only if it's their surname, or so he told me was the law in Canada). The difficulty he imposed on some of our infrastructure was justified in his mind by the much simpler name that we could use (both in person and in email). Upon hearing this explanation, I agreed that it was justified, because I saw his full name as given at birth, and I would never be able to remember it, either for pronounciation or for trying to send email to him (and he ended up reporting to me - I'd never be able to send him work assignments!).
This encounter has picqued much of my interest in how people deal with their own names, so I, too, am curious here as to the actual "why". That said, I see no reason to black out the answer to allow for more guesses - this isn't (or shouldn't be) a challenge or obfu...