Raw beginners don't notice my feints, so they don't respond to them. They don't attack from efficient angles, which means that their attacks come in unexpectedly. They're perfectly willing to attack into my attack, which means that I must get used to continuing, and winning the point on right-of-way (I fence foil. Do I read like a Cossack or a sadist (saber or epee)?), which I dislike for practical reasons. They parry with ludicrous force, and get over-excited and jab me in various off-target areas which are sensitive. Also, they often score against me, which is by far th most irritating aspect of the whole thing.
Beginners with a bit of practice respond nicely to my feints. They attack predictably. They try to hit me in the torso, not, say, the knee.
I suppose the point of this post is just to stress the old martial arts truism: "There is no defense against the random."