My daughter has special needs but she did walk on her knees for a long time before she pulled to a stand. It was about balance, an understanding of her vestibular motion (how to stand without falling over). She needed more trunk (spine) control. We did lots of exercises with her arms over her head, tied ribbons to a plastic fly swatter for her to wave, encouraged her to play while on her knees where she couldn't see around her so she had to rely on her own sense of balance (stand in front of her and hold a toy with buttons for her to push). My daughter also has visual issues and that made it hard for her with the balance too because you rely on visual stimuli to get a sense of where in space your body is.

It sounds like the parents might be guilty of carrying her when it wasn't necessary as in if she whined enough they went and picked her up instead of insisting she crawl over so some of it is likely a learned behaviour. Not all kids are walking by 14 months and espcially in recent years with the use of exersaucers, high chairs, swings etc that confine the child and dont' let them exercise and learn balance.