People who are familiar with the field don't care about these journals. The problem is that poorly fact-checked popular media are more than happy to cite these journals in click-bait articles touting "A Miraculous Cure for Pancreatic Cancer", which are widely disseminated to readers who don't have the scientific background to evaluate them rigorously. They see that the research was published in The Foobar Journal of Crypto-Oncology, and assume that it's reliable.

And if no reputable journal has published a cure for pancreatic cancer yet, the junk-journal articles will be at the top of the search results.