To limit the probability of the inadequate splicing of ceiling joists, which could lead to ceiling joist splices being unable to resist the tension forces imposed by expected gravity and lateral loads on rafters, which could lead to the lower end of rafters moving outward, which could lead to:
This is to limit the probability of the excessive deflection of supporting walls, which could lead to compromised operation of doors or windows required for egress in an emergency, which could lead to harm to persons.