To limit the probability of differential vertical movement of soil beneath and between the foundations of dwelling units and the foundations of structurally-attached garages or carports, which could lead to damage to foundations.
This is to limit the probability of an inability to support vertical building loads or lateral earth loads, which could lead to:
For floors and elements supporting floors, this is to limit the probability of excessive deflection and vibration, which could lead to persons losing their balance, tripping or falling, which could lead to harm to persons.