When you make a protein shake, look at how big that scoop is. Now, imagine trying to condense that mass into a pill form while still making it digestible. You would either have a horse pill or a dozen small ones, both having the problems, so common in supplements, of trying to fit a lot of mass into a tiny volume.
If you are sick of the flavor, get a less sweet powder option. If you are drinking the pre-mixed stuff they sell in stores, consider buying a giant tub of powder, throwing a dry scoop into an empty plastic shaker, and taking that with you to the gym. It will taste better than muscle milk and consume fewer plastic bottles.