DAS, a lot probably has to do with the size of the freshwater environment itself -- it's limited. Life in a small lake or pond is much different than the life of a fish in the open ocean. Whether it's over-fishing or something like water quality -- the effects are magnified in a smaller body of water.

It's probably a combination of all of that, plus the fact that the bass is one of the most popular game fish in the U.S.