Problems I have With This Joke

The Joke: "I see," said the blind man to his deaf wife walking their dog with no legs.

• The deaf woman knows her husband is blind. She knows what he means.
• Either the blind man learned ASL (difficult, but not impossible) or his deaf wife was lip reading.
• Their dog probably has some mobility device to compensate for the lack of legs.
• Omitting any mention of disability makes this an ordinary scene.
• Can't a man and his wife walk their dog?