Seriously. You need your ass for lots of important things.
On the other hand, laughing it off does open up alternative responses to being ordered to "get your ass in/over here."
well, provided the other parts of the body are still there, you might be able to get by. Put an extra pillow anywhere you might plan to sit, and you may need to wear some sort of protection in your pants to prevent matter that might escape your colon from damaging your pants. (no ass = no sphincter).
Other than that, I can't think of much that it really does.