yeah, memory usage is probably only erason why many of attributes are stored only in ItemType class, not in every object of Item class, in global tibia emulator every attributes can be stored this way(it can save some memory), but I guess there are also many other things that have something to do with memory usage(map storing in memory probably, players are saved when they log out what is clone friendly but saves tons of memory if you compare it to "load all players on startup")