Now, of course scientists could run a reputable journal for free or on donations. However, once you have achieved a reputable status with your journal, it becomes something that can be milked for money. And generally people fail to resist that temptation.
Even if they resisted, they still have the entire academic publishing industry very scared, and as we can see, these are people who aren't afraid to use the dirtiest tactics to protect their position.
Even though the status quo is strong, it can be dismantled.
Personally, I think it's always a mistake to build a business into government policy. It uses the government to protect the business from the free market, and the business to protect the government from public influence or public transparency