Because Graal is a hobby and something they enjoy doing.

The people who actually invest time and work into Graal (developers) already have jobs in the technology field or the field they enjoy doing, most developers have been involved with Graal for years it's just something they enjoy doing in their spare time, seeing your work become something people come to enjoy is also a pretty good feeling.

Being a basic GP there aren't really any opportunities out there because being an administrator on a game is not a career choice.