This software analogy is more flawed than most. Both of the other things have timed contests exactly like a hackathon. Cooking has Iron Chef and all of those variants, and film has their own 24-hour (or X-hour) contests where teams make a film along a certain theme. In all cases, it's not so much about the finished product as it is about the process, and a way to measure the abilities of the contestants. And if the challenge is good enough, a way to grow in that field.