What proponents of "open access science" fail to realize is that science is a business like any other, and a very big one involving lots of money. Like in any business, some form of marketing and reputation management is key. Academic publishers provide essential marketing services: filtering, sorting, and branding. You self publish, and most people regard you as a kook. You publish in Nature, and suddenly you're someone worth reading. Branding, credentialing, signaling, all these things are just as important if not more so in science than in any other field, and that's the service academic publishers provide.

At the end of the day, nobody is holding a gun to the heads of professors forcing them to publish in these journals. These are freely-negotiated agreements between researchers and publishers. The reason researchers continue to support the existing system is that it serves their purposes and furthers their careers. Any alternative system will have to provide similar benefits.