Because its really expensive to buy Exp from other sources ? When someone would find a bug, where he could generate gold, and would just use it all for his gear, it would not be gamebreaking neither, as long he only gears his own character with it. Or when you would just find something, which would give you for example 1k sacred vials. I think getting max level in for example a month by farming 800m a day would be more valueable than these vials for moth people with maxgear.