To limit the probability of inadequate capacity, rigidity or withdrawal resistance, which could lead to premature failure of nailed joints, which could lead to compromised strength of wood members, which could lead to an inability to resist expected vertical or lateral loads, which could lead to fastened elements detaching from supporting members.
Where assemblies are required to provide fire resistance, this is to limit the probability of compromised fire resistance of the assembly, which could lead to harm to persons.