The questions ‘What constitutes a good health care decision?’, and, by extension, ‘What constitutes good healthcare decision support?’ continue to be asked. The most developed answers focus largely, often exclusively, on the quality of the ‘deliberation’ component as the determinant of the quality of the decision or decision aid. We argue that these answers and resulting aids reflect the preferences of healthcare professionals and aid developers and that these preferences are closely aligned with their interests. Some interests are material, but many professional, institutional, intellectual, methodological, and ethical. Successful promotion of a particular preference-sensitive, interest-conflicted decision aid does not change its ontological nature. Conflicts of interest are therefore universal and of concern only when this ontology is denied and if aids based on alternative interest-based preferences, such as technologies involving numerical analytic calculation, are subjected to discrimination.