While most agree that traditional TCM brews (not the commercial, sweetened ones) may not usually be appetising, some brews are particularly more bitter than others.
This is because the taste of TCM herbs is closely related to the medicinal property of the herb. For example, sweet herbs like red dates tend to be nourishing, sour herbs like dark plums tend have an astringent effect, and bitter herbs like "huang lian" tend to be cooling and clearing.
Therefore, generally speaking, patients with excess heat are more likely to be prescribed bitter herbs to clear away the heat, as compared to patients who have deficiency syndromes instead, thus having to drink more bitter brews.
Evidently, the Chinese were right in saying "'凉' 药苦口". ;)
这就是名副其实的“ ’凉‘ 药苦口”。;)