Veterinary medicine has become a big industry with joint replacements, chemotherapy and any number of other silly (IMO) procedures inflicted on animals who couldn't possibly understand the need for such discomfort.  We probably spend more on our pets than many countries spend on human health care.  My beloved dog is a healthy 13-1/2 years old and there is no way I would selfishly put him through painful and frightening interventions just to keep him alive if he had cancer or some other terminal illness. As you say, keep him comfortable, loved and at home where he feels safe.