Because the amount of pencil-whipped "peer review" feedback I've received could fit in a shoe box, because many "reviewers" are looking for the CV credit for their role and not so much the actual effort of reviewing.
And there's no way to call them out on their laziness except maybe to not submit to their publication again and warn others against it too.
And, to defend their lack of review, all they need to say to the editor anyway is: "I didn't see it that way."
I never understood how peer reviewers are supposed to "validate" a paper and how they’re tacitly thought to be doing so by the general public. Authors make claims based on data reviewers don’t have direct access to, from experiments they obviously can’t supervise the execution. They’re forced to accept the claims at face value. In my experience (and I’ve been on both sides), it’s more about overall quality and impact. Journals don’t want badly written papers on unremarkable topics. It’s closer to being a harsh anonymous editor than a real safeguard of “science™.”
I would say peer review is guaranteed to have major problems either with researchers writing what their peers will approve and reviewers being afraid to diverge from the party lines.
