It’s not. But some of the valuable skills you’ll pick up from this sort of format (on top of some portfolio pieces, bragging rights, and improving your own discipline specific skills) are good communication, time and project management, realistic scoping, leadership and teamwork, and the ability to rapidly prototype—all skills that game development companies (or any company) are looking for nowadays, regardless of what discipline you’re in or what degree you have.
Most Game Jams are 48 hours (some are even shorter at 24 hours!). A lot of the people who go to Game Jams have no experience to start with either! If they can make a game in 48 hours, you can make one in two weeks.