attributes containing subordinate attributes

The TREX spec allows patterns for attributes 
containing subordinate attributes.   For example:

<attribute name="foo"><attribute name="bar"><anyString/></attribute></attribute>

I do not see any values in allowing attributes to contain subordinate attributes.
Certainly, this is not allowed in XML 1.0.

I would argue that such patterns are useless, doubtful, and should be dropped.

Cheers,

Makoto