It may not pay the rent or put food on the table, but seeing your name in the credits of a movie your friends watched or a game they played is a perk that has real value. Writing a technical book rarely pays the bills either but it's the same story of getting to see your name on the shelf, and maaaybe it leads to getting on a conference panel or something at some point but really you're doing a lot of labour for far below minimum wage just to be able to say you did (as I did for Apress when I was 20 years old... and it landed me an internship at Google, so there you go).