It's true that this game relies on RNG, but imo there should be some kind of system like seal scrolls, where after a certain number of boxes you get something good.
About this conspiracy, I think I somewhat confirm that I noticed lower level players getting good drops while us getting nothing.
My 2nd character always has better luck, and a friend that joined us only much later in our server has won Tendo twice in Lucky Stars. So ye....there might be something like that coded inside the game to attract lower levels to spend, and also motive the rest of us to spend as well.