The field of study is not supposed to be “do we like this sort of people and get along well with them” or “are they well adapted behaviorally to be productive members of society” but rather an actual set of illnesses which can be diagnosed, treated, and conceivably cured. We do in fact prescribe powerful pharmacological agents based on these criteria, after all.
And yet, as the Director of the NIMH rightly laments, "DSM diagnoses are based on a consensus about clusters of clinical symptoms, not any objective laboratory measure."
It is in essence a type of culture war hiding behind a so-called diagnostic manual. In that sense it is more aptly described as a dictionary, whose lexicon is revised more based on their perceived common usage more than hard scientific study.