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