Active v. passive euthanasia: why keep the distinction?

Society's decision to distinguish between active and passive euthanasia may have been a pragmatic one. Public opinion polls show a substantial majority of Americans favoring the right of the terminally ill to refuse treatment and many favoring active euthanasia for the comatose and terminally ill. Some active euthanasia proponents would like to erase the distinction, but society seems to want to preserve as many restraints against killing as possible.