Maybe because Metacam isn't superior!! If you overdose your dog with metacam by just a little, it will have serious problems. Don't fall for that convenient liquid dosing crap. The reason it comes in liquid form is because it has to be given accurately... and this is because it's margin of safety is so narrow. Read the PI for god sake.
Rimadyl will always be the first choice, especially since Drmx is shelved for a while! Mtcm will always have the stinkma as the "vomiting drug" The truth is hard ... we all know.