Short answer: scientific studies are sometimes misreported by the media because headlines reward simplicity, novelty, conflict, and certainty, while real research is usually narrow, conditional, and uncertain.
A study may make a modest claim, while a headline turns it into a breakthrough. An observational association may be reported as a cause. A result in mice may be written as if it applies directly to humans. A small early study may be described as if it settles a question.
Why distortion happens
Journalists work under time pressure and need stories that readers will open. Press releases may already exaggerate the finding before journalists see it. Universities and journals benefit from attention. Researchers may also be tempted to frame their work dramatically because visibility can help careers and funding.
Science itself is full of caveats: sample size, confidence intervals, limitations, mechanisms, uncertainty, and alternative explanations. Those caveats do not always survive the journey into a short article or social media post.
How to read science news
Ask whether the report links to the original study. Check whether the study was in humans, animals, cells, or a model. Look for the sample size, study design, and whether the result was observational or experimental. Notice whether the article includes independent expert comment.
Good science journalism explains the limits as well as the headline. A careful reader should become suspicious when a report makes a study sound too clean, too final, or too useful for a culture-war argument.