I think it is a waste of food as well ... But I doubt it is the case that people waste the rest of the shark. If that was the case, shark would be cheaper than haddock and cod in the supermarket. I think the footage that you and I have seen is simple liberal, Green Peace propaganda.
http://www.youtube.com/watch?v=C0p_LdfgmxQ
http://www.youtube.com/watch?v=SLmS4J_Gd40
We can take issue with the numbers cited, but not that the practice occurs.