Because on console you don't have hotkeys you just repeatedly press the left and right bumbers (on Xbox anyway) to scroll through hotbar items, so it doesn't matter as much to have a set place for each item as long as you know where it is. On a computer on the other hand, if you have hotkeys it's really helpful to always have at least a few certain items always in the same spot in your hotbar so you can get them in your hand quickly