I agree and I'm fighting them on this one. My (stubborn) father swears he'll make it without one. I keep pushing for them to take our double. He doesn't want to mess with it on the plane. I'm to the point of paying for it myself and if the use it, they use it. If not, oh well - they had it just in case.
My family has a long history of travelling with "broken" family members - usually myself (I have had multiple surgeries on feet, ankles, knees - around 13 by the time I was 18, starting at 6) and we've done okay, this is the first trip where it's been mom on the DL.
I love this board and I'm so thankful you are here to share an immense wealth of information! I've also loved reading about the visually impaired threads - I work with 2 kids who are blind (LCA) and hope that one day they'll make it to the World. At least I know where to send them for info.