In the forums of a popular motorcycle site, the question, "Do I really need hip protection?" is answered with the response, "You only need to protect the pieces you want to keep." That advice is especially true with your hips, second only to collarbone fractures and broken pelvises in injury statistics. This is partly because a hard hit to anywhere in your lower body channels itself into your pelvis, and partly because we tend to bounce and slide especially well on the parts that usually sit in the saddle.
Take a look at any online video of sliding motorcycle crashes and you'll see that in far more than half, the rider ends up skidding on his or her derriere. Another quick Internet search returns pictures of the consequences: road rash that eats through jeans as if they were mist.
So armor up those hips -- either make sure your riding pants include hip padding or layer up your own padding with hip-specific inserts.