Guard placement is an important thing to think about. The distance from your body greatly effects how much of you is covered by your defense. We call this the cone of defense.
The coverage of your guard isn’t just the same shape of your shield. It extends at angles around your guard, these angles are effected by the size, shape and orientation of your shield. As shown in the images comparing two different sword and buckler stances. As you can see the further away from you the beginning of your guard is the more coverage it gives your body.
It may appear that this would only effect straight attacks, such as thrusts, but this concept can be applied in the same way with other attack too. With your guard further away from you you have more time to make the block before it can get the angel to reach you.