The key lies in the word "waste", which can be said to be expenditure, cost and consumption, and changes according to the meaning of the latter nouns.
Personal understanding is that learning calligraphy requires constant practice and consumes a lot of paper, while learning medical skills depends on gaining successful experience from patients' failure examples and going through many patients (in layman's terms, there may be a lot of life accumulation). How important clinical experience is to a doctor and so on. Nothing can be done overnight. Long-term practice and accumulated experience can master a major.