Why PubMed and MEDLINE indexing are so important:

The system of Evidence Based Medicine creates checks and balances and a benchmark for credibility. Researchers, the Universities that employ them, Medical Journals, and the Peer-Review boards of those journals are all part of the checks and balances process to ensure the quality of published articles. The final step to create a benchmark for credibility is to ensure that the journal itself is credible; which is a role of the National Institute of Health and MEDLINE.

Medline is the largest component of PubMed, the U.S. National Library of Medicine’s database of biomedical citations and abstracts. Journals are only indexed by MEDLINE after meeting specific standards related to the quality of content and quality of editorial work, and the criteria considered to determine whether or not to index a journal for MEDLINE are significant. The final decision is made by the Director of the National Library of Medicine, based on considerations of both scientific policy and scientific quality. The Board of Regents of the Library sets policy for the Library. The Literature Selection Technical Review Committee has been established to review journal titles and assess the quality of their contents.
U.S. National Library of Medicine MEDLINE Journal Selection

Articles published in journals that are indexed by MEDLINE have met important standards for credibility, allowing the medical community to depart from treatment arising from personal opinions and rely instead on the strength of Evidence Based Medicine.