This is Dublin Core XML. Note how every field wrapper clearly indicates the content of the field. If I want all title fields, for example, I write code to retrieve all dc:title nodes. Easy.
This is MarcXML. Note how every field wrapper has the same name and is only differentiated by numeric tag attributes. To get title fields, I have to look at every datafield, check if the tag of that field == 245, and then retrieve all subfields.
Don't even get me started on retrieving 880 fields and the nonsense way they correspond to other fields. There are better ways to store metadata than Marc.