There is a cost to doing this though, that's the point. Who gets the money is in many ways not relevant to the central point. You are not paying for a single paper to be reviewed. You're paying for all of the rejected ones too. The high APCs of even non-profit publishers is a key point to show that costs end up being quite high.

> All that activity the journals do prior to publication can probably be streamlined and solved a lot more efficiently

It's a huge industry though, and so saving money can translate to huge profit increases. While not competitive like other marketplaces are, I'm sure these places like money and so have their own drive to cut costs. You can't just throw technology or "social platform" at a problem and hope costs go down.