Because there is science, and there's science, and for a layperson it can be impossible to tell the two apart.
Science 1 is the scientific method we all love since we are toddlers: we try something out, then again, then again, then again - and from that we learn something.
Science 2 is an impostor who has aligned with the oppressors. It uses the language and the coats of Science 1, but will claim cigarettes are healthy or glyphosate is harmless for whoever can pay more.