maxOccurs and minOccurs default values

The default value for maxOccurs is stated as being "unbounded" and for 
minOccurs is stated to be zero.

Is there a reason for departing from the (implicit?) practice in DTDs and (?) 
in W3C XML Schema that a default value is exactly 1? 

If so, perhaps it could be stated in the WD.

Andrew Watt