If a journal finds that it's getting more papers than peer reviewers are willing to go through, how does a more heavyweight, synchronous review process solve the problem? Many researchers already find peer review requests annoying, they're not going to agree to hold a bunch of video calls.
Big part of the annoyance is that journals demand basically free labor - while costing massive amount of money if you want to read them.
A review call might just end up being less work then reading a lot of slop papers.