I think it depends a great deal on what type of data you're talking about. If it's a magazine article then yes it's essentially a stream of text and 2D formatt

I think it depends a great deal on what type of data you're talking about. If it's a magazine article then yes it's essentially a stream of text and 2D formatting is probably secondary. However if it's tabular data then the 2D formatting is essential to its interpretation. A lot of the text we encounter in the world does depend to a significant extent on 2D layout to facilitate its comprehension. Examples include many (perhaps most) websites, product labels, tax forms and receipts. None of that is the fault of the PDF format which is intended to faithfully represent 2D layouts. As you mention, if the goal is accurate labeling of content other formats exist which are more suitable to that purpose (though I think the concept of separating content from presentation has always worked better in theory than in practice).