Autobot N
Well-Known Member
Because its strategy is to use only that move ASAP. It's holding a Choice Scarf which will raise its base speed by 50% and lock it into only using one move anyway. That allows it to move faster than most Pokemon (unless you also have a Choice Scarf attached) and slam you with a full power Eruption.
One of the rematches with Roark has the same thing. His Relicanth is choiced and has only Head Smash