Well, like pretty much everyone else, it seems, I voted 'because I enjoy it'. If there had been a 'because I'm driven to' I'd probably have chosen that - but that would arguably just have been pretentious. :-)

But of course all this doesn't actually address Martin Parr's point - people could just enjoy reproducing familiar pictures, and in general I think there is far too much of that in amateur photography. It's actually the thing I find most disheartening about it - I want to see stimulating and original images but so often I'm just presented with the same tired old subjects. I won't bother going through it all again here, but I will just cite a couple of threads from the last year or so which illustrate precisely this point:

Buachaille Etive Mor Watch

Most over-photographed locations