Simple Question

I appologize if this is the wrong place to send this question.

My question is:

What was the fundamental motivation for having attributes in an XML 
Document ? Whatever that can be contained in an attribute of an element 
can be contained within a sub element. If I model an XML Document as a 
Java object, would I need to distinguish between the elements and 
attributes ? Moreover, why was it decided that attributes can only be of 
a simple type ?

thanks,
Ram