Loyalty vs. Royalties: Author as collaborator or contractor?

If authors are becoming contractors rather than partners, that changes the role of both author and publisher in a big way. But why is it happening, and is it yet reflected in how publishers work?

If the author is no longer a collaborator, then the publisher must take on that role and so in effect become the ‘master’ author to whom they subcontract the details. This would be analogous to those master painters of old who would paint the head and hands of a portrait, leaving the sitter’s clothing and the background details to be filled in by their apprentices.