Why did folk music compilation begin in Song Dynasty?

First of all, editing music is a very costly and energetic thing. It is impossible without a certain economic foundation. Song Dynasty was a relatively rich dynasty, and wealth was hidden among the people, so the people had the ability to arrange music. In addition, after the Eastern Jin Dynasty moved to the south and the turmoil in the late Tang Dynasty, many people were eager to get to the bottom of it and find out the ins and outs of the family. In particular, the spectrum needs to be trimmed. This is the motivation and motivation for Song people to start arranging folk music.