the skinner box approach does not work when the player can simply make a trade rather then have to gamble on the drop/prize. Bungie have built in payout ratios that give just enough to keep you chasing the next "win" . worse still they have you playing a number of different vegas style games.. that is why there are so many different currencies and prizes... it is also why a engrams require that they be opened... first you win one then you have to roll for your prize... there are far too many layers for me to go through but maybe someone has detailed it somewhere... It is a very good trap, but it is still a trap. It is designed to ensure whenever you reach one goal you are halfway to another and always there is a chance of a good drop while completing a chore and of course the random nature of "events" . These things are not designed for good game play they are designed to keep the player motivated with a series of overlapping rewards. This is why your stuff gets debased, they need you chasing your tail ..