I don't thing hackathons are for building a software that will be shipping right away. I think the objective of hackatons is to do quick experimentations, be as creative as you can and see if something interesting and new comes out of it in a few hours.

If something doesn't exist you don't even know if it's possible to accomplish. In a normal working schedule it would be very difficult for you to get time to work on something nobody-knows-if-it-will-work-or-not. Besides, your boss will not be very happy if you 'waste' time on that.

So the goal of hackatons, in my opinion, is to spend some time to travel on uncharted seas...you may find nothing...you may discover America. But you have only discovered it, not conquered it...that will take more time :)