Copyright is the entity allowing creative artists to make a living from their work. Distributors/Publishers are the middlemen that can help or hinder you in making money from your work. Assigning all your rights to a single entity is a recipe for suicide.
Monopolies have no incentive to work hard for you. Think I am wrong? Just ask your cell phone company.
Nina Paley writes this at Techdirt:
Middlemen will only have monopolies if artists keep granting them. They’re not going to give them up on their own. It falls on us artists to simply refuse to grant these monopolies in the first place. A copyleft license sends a clear,simple,and non-negotiable message to middlemen that they need to innovate and compete to profit from the work. Only we artists can supply the incentives they need to do their jobs well;and we can only do that by refusing monopolies.
The Problem Isn’t Middlemen,It’s Monopolies | Techdirt.
If a middleman says they need exclusivity,run away.