pixel_player4367261 partly because its a material sink for those with excess mats to convert into gems...would be silly of the devs to make it easy to collect tons of gems, with little effort, on an infinite contractor even though it is pretty easy to collect gem in other parts of the game
the gems are increasing slightly as you progress...at contract 50 you get 50 then 10 gems till 100 when you get 100 gems, its 20 gems a contract after that
http://trainstation.wikia.com/wiki/Richard