Game jams (similar to hackathons) are great for applying what you already know but with a new group of people. They're much harder if you _dont_ know what your doing (contrary to what you suggest).
I've found that the group really makes the experience, and find them less fun for the tech and more fun for learning about the people through the work and a team project without the constraints of a corporation.
And generally, it's not just people who aren't tied up in this that will participate, but people who will make time to do something exciting and form an interesting connection.
I think that's because games are an art and highly creative. You're crafting an experience, usually a combination of story and gameplay.
Regular software projects can also be creative, but almost all software is pure CRUD at the heart.
The next issue is the required time for the MVP. For a game, you can validate the base game loop quiet quickly.
It's a lot harder to validate wherever regular software is actually viable, because you usually need to basically finish it entirely before the UX can really be validated if a mock-up doesn't suffice
I've found that the group really makes the experience, and find them less fun for the tech and more fun for learning about the people through the work and a team project without the constraints of a corporation.
And generally, it's not just people who aren't tied up in this that will participate, but people who will make time to do something exciting and form an interesting connection.