Sally on a swing Why did Sally fall off the swing? Because she's got no arms. Why didn't she get up? Because she has no friends.
Why are making comments on an amputee?
It's a joke. She doesn't have arms, right?
People with disabilities are very capable and it is hurtful to think they are useless. You could become disabled later in life due to an accident or disease and you would not like it if people suddenly thought you were now useless.