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.
That is true across all fields, not just for publishing scientific papers. That's why we need a true cooperative economy, that is an economy of cooperatives which do not compete with one another but promote active cooperation to reduce the overall competition/privatization in society.