The technical answer is that this is an unranked jam with a busy host, so no real rewards.
To add on to what blueice15 said, I join jams to get practice. I started my game dev journey only two months ago! Since then, I've entered four jams with two more on the way, and I learn something new each time. werewolf minesweeper was my first time using a heavy-ish amount of CSS in Twine, for example. I also join just for the joy of creating and the deadlines that help motivate me, since game dev is something that helps me more than I can express as someone with psychiatric disabilities and is a part of my self-care.
What you get out of a jam, is ultimately, a game. And that game can be a reward in itself, if you look at it right. :)