"Mistakes are cheap because there’s no external pressure to perform, so developers can take risks and experiment without fear of repercussions or embarrassment"
I've been lucky enough to have jobs in the past that allotted a bunch of time for learning, but I know a ton of people who don't have that luxury.
For students, I'm sure hackathons are a great change of pace from what they're doing in class too. Nobody puts a grade on your hackathon project after all :)
What a great way to learn :)