Roughly 30% of published, peer-reviewed scientific studies are estimated to be not reproducible. Because nobody takes peer reviews seriously and everyone is just rewarded for publishing, no matter how much of it is garbage.

Remember the "chocolate helps you lose weight" study that went through every stupid newspaper? It was obvious garbage, employing p-hacking, using a fake researcher's name, using a made-up university institute. And yet it went through peer review without issue, was published in a journal and was picked up by every newspaper under the sun.

Then the author stepped forward and said he only created this fake study to show how easy it is to publish a garbage paper. The thing he didn't expect was that nobody cared. Nobody printed anything about him retracting his own obviously fake study. No consequences at all were taken to his finding.

Because everyone is incentivized to publish every piece of toilet paper they can find, and nobody cares about the quality.