Powerlifting for 10 here. Just hit 40, and I'm stronger than I've ever been. What scared me into seriously exercising when I hit 30 was that it started being painful for me to walk up a single flight of stairs, and when I went to my doctor she looked at me with utter disdain and handed me a sheet of basic bodyweight exercises and sent me packing...
Now my 1RM squat is 192.5kg / 424lbs and my knees never give me trouble any more.
I think quite a few of us get into lifting partly because we need something to counteract the damage office jobs and sedentary lifestyles out of work do, and partly because it's something that fits the hacker mindset - weight lifting, whether oly or powerlifting or body building, lets you endlessly tweak programs and diets and measure results fairly precisely.