Drop rarity in MMOs is a mechanic to get you to play longer without actually experiencing character progression. It's just artificially lengthening game-time, and drip-feeding rewards sporadically to condition you into gambling on the rates for the high you get when the RNG rolls in your favour. It's the "just one more; it could drop on this next kill" attitude. You play longer, you stay longer, you create personal goals that justify your grind, and your spending potential increases based on that time.
In that sense, iRO benefits greeeaaaaatly from you taking the longest time possible to farm what you're looking for. They won't modify the rate or give you a trade-in option.
In order to milk it even harder, gum consumables were added to the Cash Shop that increase your potential (important word as it doesn't guarantee you'll get value for money) drop rate thus theoretically reducing time spent grinding in exchange for cash to be granted the opportunity. The time limits are imposed to both ensure you buy more, and to keep you invested for that duration. Goes hand in hand with reward-based reinforcement and facilitates extended play by locking you into a sort of pseudo-contract since your crazy, intrinsically human purplemonekydishwasher logic will compel you make the most of that time.
So if you're not using gum, go buy some and pop them today! You may possibly get more chills!
Edit: also VIP. Works in much the same way but locks you in for longer <3
Edited by AlmrOfAtlas, 02 July 2015 - 09:28 PM.