To limit the probability of inadequate strength in the prevailing direction of shrinkage, which could lead to the excessive cracking of stucco.
Where stucco is applied to masonry chimneys, this is to limit the probability of precipitation or meltwater ingress, which could lead to the premature failure of chimney liners, which could lead to the escape of heat or flames, which could lead to the ignition of combustible building components, which could lead to harm to persons.