To limit the probability that ledger boards will not be adequately attached, which could lead to inadequate end support of floor joists, which could lead to an inability to resist expected gravity loads, which could lead to the excessive movement, deformation or failure of floor assemblies.
This is to limit the probability of:
For floors and elements supporting floors, this is to limit the probability of persons losing their balance, tripping or falling, which could lead to harm to persons.