I assume it was because QR codes are futureish and someone claimed this was innovative
Because the map might change in the future. You can keep the link the same, but update the content.
Or print a new map?
Because you can't take that map with you.
no but you can take a picture of that map
However you can't zoom, adjust layers, and make queries of a picture of a map. Ideally you would have both. Print the map... Put a QR to the enhanced digital version in the corner.
Because maps often need updating. What you're saying is kind of like saying "why have a link when you can just copy the page directly?"