Homeopathic Profit

If traditional Chinese remedies and homeopathic medicines worked so well, why don't large pharmaceutical companies sell them as well? If something like St. John's wort is just as effective as Prozac in the treatment of depression, why doesn't Pfizer have their own line of products? Why don't they spend a fraction of their billion dollar R&D budget to isolate the active ingredient, patent it, and then sell it? Maybe because there really is no real benefit to these "remedies".