Comment by djmips

People like to program on tasks that aren't given to them, to practice their craft in a less restricted form than professional life usually allows. So they make things for themselves and its natural that those things are what they are familiar with and enjoy. So you often meet the programmer, almost never from the game industry, who wants to make his or her own game engine. It's about as likely to be a productive endeavor as making your own spreadsheet program.