I just looked at all of my mom's and my jackets, and you're right some of them do not have size labels. The ones that did not have sizes are the regular quilted jackets (all 3 types: zipper, small snap button, and large button) and a zip-front denim jacket.
The ones that do have size labels are a puffy ski jacket and a fleece-lined quilted jacket that has raccoon fur trim on the hood.
I wonder why too?