Thanks for your reply!
Well, I think I can safely assume that none of us truly understands the mechanics behind drop rates and in what ways charms and gems affect them. Let's say you get a single sprite out of every 100 upgrade chest (brown boxes), this means every upgrade chest has 1% to get a sprite and 99% to get something else, like Grade B scrolls. By applying charms and gems, do they amplify the 1% at the expense of the other 99% (i.e. at + 500% drop rate, 5% sprite & 95% B scrolls)? Or do they actually not affect this ratio at all? This really begs the question: does improving drop rates really help, or actually a hoax that simply acts as a gold sink? *Conspiracy theory intensifies*. Because none of us understands how charms and gems affect drop rates of specific items, the underlying mechanisms only can be speculated. One thing that we can really conclude is that charms and gems does improve something by ensuring every mob drops at least something (achievable using just 25% or 50% drop charms / gems), and without charms and gems, 10-20% of the time the mob doesn't drop anything at all. But by going beyond that + 25-50% drop rate, it is unsure whether drop rates of items actually improve.
However, the point is that higher level sprites have ridiculously low chance to drop, particularly levels 51 and beyond. This means that the drop rates of sprites have been tweaked to be like this on purpose, which is antithetical to the whole point of this game: SPRITES. This game is about obtaining sprites and training them to help you in your journey, so majority of the player's time should be training sprites, NOT farming for sprites. And if even the application of charms and gems, which are the only thinkable way to help, actually do not increase the chance of sprites dropping, then this game is simply trying to test players' patience, many of whom I doubt have much to speak of. Many players don't even bother to obtain and train sprites and simply buy equipment from other players, which causes huge inflation to prices for all the materials required for crafting.
Sprite training and crafting already takes forever, there is absolutely no reason for players to suffer the laughable sprite drop rates.