It's cultural. Japan has a cultural of reciprocal gift giving that underpins this entire exchange. Basically it's a decentralizing force It prevents a doom loop

It's cultural. Japan has a cultural of reciprocal gift giving that underpins this entire exchange. Basically it's a decentralizing force It prevents a doom loop where everyone moves to Tokyo because that's where all the resources are because everyone moves to Tokyo as the rest of the country hollows out