why don't people ever do that
That's why a lot of addons die, like rtb because they are too lazy to pass the project/addon
Are you serious?!?!
Ahem, but you obviously have never worked on a large project. The project becomes your responsibility. You can't just hand it off, because you get a exact image of how the project would turn out which can in no way be achieved by someone else.
Also, RTB went down because Ephiliates was tired of Blockland's slow development and i quote, was tired of providing a professional service to a unprofessional game.