I think the Japanese are very accustomed to using everything; here, people have gotten away from that. The *older folks* know what that it all about and cling to old habits; especially if they lived through the Depression.
When I had a wood range in my kitchen [it would warm us from Labor Day to Memorial Day]; I kept stock pots simmering 24/7, all winter; never wasted any scrap.
Now, I don’t have that facility.
Much scrap goes in the dog’s bowl.
I remember the Japanese dogs would eat anything. Pet food is expensive there so they feed their dogs everything. I watched a guy feeding a dog raw slices off a big daikon radish and the dog gobbled it up.