Do some ribbons (left side) not have medals?

If it is ribbon in the title, not medal, then it has no medal associated.

Yes indeed, SPC John Hamilton. Some awards are ribbons only. The Army Service Ribbon is a notable example.
Sgt (Join to see)

Ribbons do not have medals, medals have ribbons.

Definitely. Quite a few ribbons do not have medal status. The AF has overseas tour ribbons (short and long), longevity ribbon, marksmanship ribbon all come to mind.

SPC John Hamilton Most Definitely. I Have 9 Ribbons but only 5 Medals. Just the Nature of the Beast. It Does Get Confusing in Full Dress with Medals and Ribbons.

As a Marine, my Combat Action Ribbon doe not have a medal. I think the Army might be the same way with some ribbons, but someone with knowledge in this area will provide you with the correct answer. In my shadow box, I have my items on one side and my Father's items on the other side. I do not have my Father's medals and will be ordering them. I only have ribbons for myself and I am also thinking of ordering these medals. Good luck.

https://www.archives.gov/personnel-records-center/awards-and-decorations

Army Service Ribbon, NCO Professional Development Ribbon, Overseas Service Ribbon, ect... are not medals.

Uh, ya, you need to read up on awards and decs!

Thank you so much!

You'll find your answer for the Army in the other responses. For the Marine Corps, there are several ribbon-only awards/decorations. I remember the first one, the Navy and Marine Corps Combat Action Ribbon, came out in 1969. We were issued the ribbon and were told that a medal would be forthcoming, since this was considered a personal decoration. As things turned out, no medal was issued - apparently the Department of the Navy thought that getting a medal designed and struck by the U.S. Mint was too much. So they went the cheap route (back in those days a ribbon cost about 25 cents), and have followed up with other ribbon-only award ribbons. Of course, unit citation awards have always been ribbon-only devices. I've always been rather contemptuous of ribbon-only award ribbons - I think they represent the route of least resistance by DoD and the Services when service men and women put in a lot of work for those awards. Of course, I have long wondered why the Services have so many ribbons and medals - most seem like participation awards. The only ones I really respect are awards for combat valor and enlisted good conduct medals.