To limit the probability that the block wall will be insufficiently stiff and strong at critical edges and openings, which could lead to an inability to resist transverse or vertical loads, which could lead to the cracking or displacement of foundation walls.
This is to limit the probability of:
For floors and elements supporting floors, this is to limit the probability of excessive deflection, which could lead to rough or uneven walking surfaces, which could lead to persons tripping or falling, which could lead to harm to persons.