@Tony it's for MMO players mainly and it's so fucking nice to have. it makes it so you never have to use the 1-0 keys for your hotbar and can just map them to your mouse instead. that way, you can focus on your movement with your left hand. maybe not as important for like, runescape, but i play phantasy star which is a full action game and you NEED to be on top of your shit. a lot of people opt to play with a controller instead.