The best example I can create for is when u have an OP weapon, the only way to entice you to grind for it in a loot based game such as Destiny or WoW, is to make a more OP weapon. Or how about this : Thorn and TLW are highly valued in Crucible for their fast TTK. If they were ascended in The Taken King, the only weapon that would entice you to trade in those guns would be one with an even faster TTK, far outpacing other weapons. And with the next iteration you need to create another weapon with an even faster TTK than before. An extreme example: Think of natural progression as a steady and gradual increase and power creep would be an exponential increase.