The benefits of strength training are for all ages, or at least have been for me, as I started barbell training after age 69. Nine months later and a few weeks from 70, I enjoy the kind of strength I have never felt--and that included years of martial arts and a variety of stuff that was just wrong for my knees and hips. Not sure that if your father hears testimonials like mine it will make a difference, but it might. And this coming from someone who ten years ago had a rotator cuff repair, meniscus repairs in both knees and a repair of a torn distal biceps tendon six years ago. The reason most people dismiss barbell training is because not many trainers know how to teach it, especially overhead work, where most gyms are too concerned with injuries because the people who own/run them do not know about barbell training. My gym has a lot of trainers, but only a few allowed to teach overhead movements. The four squat racks and four platforms Olympic stuff are usually open in the biggest and otherwise busiest gym in Boston.
IMHO, I believe that my generation needs more advocates like Mr. Rippitoe or Dr. Sullivan who get more publicity. What is unique about barbell training in my experience is that one can experience reasonably fast results, although the plateaus might arrive just as fast and that the challenge to perfect the technical movements is fun.