A certain texan ranger would probably just say "for the damn glory" but if you don't subscribe to that point of view then how about in order to see some wonders and to make a small fortune in exploration data (and raise your exploration rank a notch or two) while doing so which you can spread around when you get back in order to earn reputation with numerous different factions?
Been pondering on this a bit - I've been stuck out near the core for far too long now. It's got to the point that I'm thinking it may be worth waiting (and exploring) till powerplay drops. I'm sure there will be powers that want exploration data, which may well make whatever data is already on board doubly valuable....