A statement from STHoldings reads:
As a distributor we have to do what is best for our labels. The majority of which do not want their music on such services because of the poor revenues and the detrimental affect on sales. Add to that the feeling that their music loses its specialness by its exploitation as a low value/free commodity. Quoting one of our labels, 'Let's keep the music special, fuck Spotify.'This follows several other labels criticizing and pulling their content from the much-hyped music streaming service Spotify, notably Century Media, Sumerian Media, and Prosthetic Records.
You can read the full article, including Spotify's response to STHoldings' withdrawal, here.