In my opinion, if you are going to attach shutters to the house, they must be fully functional as window coverings, mounted with correct hardware, including shutter dogs.
You may choose to install them only on front of the house. If side windows are visible from the street, I would put shutters on these windows, too.

I think it's fine. Why do they need to be fully functional?

Some of the decorative shutters are much too narrow for the window they are flanking and are not flattering to the overall design of the house. Other Houzzers will have different opinions from mine. Take from this what is helpful.