Branding is not value added. If I take a picture of the Mona Lisa and fudge my signature on the bottom I don't deserve credit for the origional.
RedHat and any other "Distributor" will fall face in the dust unless they can find a way to provide some product or service that is demanaded by consumers and not easily replaced by competitors. They know that. Look at the acquisitions they have already made.
As to them not explicitly saying "I take credit for it all". My retort is to say,"How are they crediting the true authors anyway". RedHat.com certainly doesn't mention the selfless contributors. If I propped a crate up in front of the Statue of Liberty and started charging admission I'd bet ya' that most people would think I owned the thing- or made it. Most people just being introduced to Linux probably think that Debian is a knockoff of RedHat.