I go to about one or two of them per year, am 36 years old, and here's what I DO like about 'generic' hackathons - that have no single sponsor:
- It's a break from my daily routine (I work from home, so its good to mingle)
- It's a lot of fun and I meet smart like-minded people.
- I get to laser focus on learning new tech without any emotional commitment.
- I know it's all for naught so I have no problem starting something and then not feeling 'guilty' about throwing it away afterwards.
- Its a serious mental challenge. I do it more for the personal competition (like golf) rather than competing against others
There are several other reasons, but those are the top for me. I never going in expecting to win (and I never do), so treating it like a weekend of nonsense probably helps.