It's related to the concept of Mottainai (もったいない, 勿体無い) in Japanese culture. Where any waste is considered bad, specially related to food. https://en.wikipedia.org/wiki/Mottainai
There is a similar concept in English culture called "waste".
In this concept, waste is viewed as a sign of affluence.
So ironically, the more one wastes the more "conservative" one is considered to be.
Pretty much the opposite of the Japanese concept of mottainai.