I know the history of xml, but just to get back to my original premise: why has a tag (a kind of key in the mind of most readers) multiple "kinds" of values/chi

I know the history of xml, but just to get back to my original premise: why has a tag (a kind of key in the mind of most readers) multiple "kinds" of values/children in parallel, especially one set that is map-shaped (attributes) while the other is array-shaped (proper children)?