Because sadly, it's the easiest way to give people a sense of accomplishment.
The term is Skinner Box. Look it up on wikipedia if you're interested (I think the proper term is Operant Conditioning Chamber, but it was created by a guy named Skinner, and it's just way easier to say.
http://en.wikipedia.org/wiki/Operant_conditioning_chamber
(I just wanted to make sure I got the name right
)
Or if you're feeling extra motivated for some Extra Credit info, give these guys a listen. Some of the smartest minds in the business if you ask me.
http://www.escapistmagazine.com/videos/view/extra-credits/2487-The-Skinner-Box
(seriously worth a listen if you like to see "behind the scenes")