The limitations on attributes tell you where you can and can't use them: the attribute names must be unique, their order cannot be significant, and both the name and the value can contain only text. Elements, by contrast, can have non-unique names, have significant ordering, and can have mixed content.
Attributes are usable in domains where they map onto data structures that follow those rules: the names and values of properties on an object, of columns in a row of a table, of entries in a dictionary. (But not if the properties aren't all value types, or the entries in the dictionary aren't strings.)
