The way my brain works it needs a nucleation site to really get going. As long as there's at least one idea or theme to start with I can riff on it and spin out an entire zine/book/work, but I need that seed idea to start. Could be something I noticed or read, some random comment or joke from a conversation, anything as long as it grabs my attention and sticks. Jams are perfect for that. They give a core idea, some constraints to work with (which is good, constraints spur creativity), and a kick to get started.
They're also just plain fun. When a jam's going you get everyone talking about their projects and sharing their progress, it's an event with its own momentum. One of my favorite parts of a jam is seeing folks get excited about what they're working on and all the different ways that they interpret the jam's theme.
My only problem with jams is I almost never finish my project by the deadline. I'm not good at creating in the typical short timeframes set for entries. As much as I love the fuck it we ball intent of jams as a challenge I can't do it. I don't like to rush and would rather miss the deadline for entries than publish something before I'm satisfied that it's finished. There have been times I've actually made the deadline, but that's because it was extended. That's fine though.
To me a jam serves as inspiration and impetus to make something that I wouldn't have otherwise. When I join one it's with the idea that I'll participate as much as I can and create, but not put pressure on myself to submit an entry. Finishing something I'm proud of is enough. It's not exactly the point of jams, but who cares?
What I'd really like is to see jams make a resurgence back up to the levels there were during the first few years of the pandemic, when it always felt like there were dozens running at once. I miss that. We should do more and bring them back.