because Vmu is important in calculating other speeds...manufacturers go to great lengths to get the lowest Vmu possible and they put a piece of wood as a tail skid or protector...Vmu is the min speed to get airborne but you are allowed a tail strike
Vr leading to V2 at the 35' screen height is imprtant too, esp with engine out...otherwise you will be faster with all engine running at screen height
for practical matters stick to V1, Vr, V2
but in the back of your mind, y ou have to have an idea about VMU...what if you take off on the wrong runway and need to get UP? or if there is traffic on your runway and you need to get over???