Because those academics were (and are) a bunch of egotistical, money-grubbing fools who would rather sell up their scientific integrity in exchange for some imaginary 'reputation' points.
Science is science, it shouldn't matter where it's published.
Science is science, it shouldn't matter where it's published.
Being published by prestigious journals isn't just about ego, it's about future career opportunities, getting grants, getting to work on things you want to work on possibly with some of the most brilliant people in your field.
I think people at the top could make things change with a massive concerted effort, and I think things will change naturally as younger people who've had a taste of open acess get access to top positions but it's too reductive to put things down to researchers' greed and ego.
If those academics had any guts, they would boycott their precious journals and strike out in a different, better direction.
They're the ones perpetuating the system, just as much as the journals themselves. It's not parasitic, it's symbiotic.
Academics hate it, but publications is the way they are measured by public institutions for, e.g., grants, or when being hired. There's no symbiosis, it has evolved in this way mostly because of decisions taken by non-academics (ministries, governments, administrative staff etc.) and nobody knows how to get out of it.
But it does, there's a limited amount of hours in the day and an infinite amount of papers. You need someone to pre-screen the torrent of crap that has an occasional jewel floating in it, and traditionally journal editors have served that role.
You don't need some pompous journal for that.
How many Open Source projects are managed by an individual, or a small dedicated group? If they can do it - by self organising! - it's baffling that some of the 'smartest' minds in the world are unable to comprehend what's going on in their field on a meta-level.
A stupid, stupid idea from people who should not be allowed to make decisions.
'Blue collar' workers figured out a way to get the message across - they formed unions, and went on strike to effect changes.
That's not to say prestigious journals are immune from bad science, just that the consequences for fraud are a bit worse and bar to clear for publishing it much higher.