I think everybody answered that it is, well, a bit absurd to regulate or rather hypocritical as many d-types wouldn't do likewise. But the OP asked "why???" and I think this is interesting to consider. For a lot of people, and d-types alike, their is a certain pleasure that comes from pleasing another person. And similarly, there is a certain displeasure in realizing you're not the only person who can fill this role. (Why I dislike zucchinis for instance)