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.
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?
Or a short URL to the map.
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?"