Pull ups are a tough exercise and I agree that 50% of men over 18 cannot do 1. I am a lean 185 and do 15. But it took a lot of work to get back to that number. Some days tendonitis in my forearm acts up, and I cannot do 4. I rest it for a week or two, and I am back in double digits. Pull ups require forearm strength, core strength, shoulder strength, lat activation and are a great measure of strength IMO. What you bench usually does not impress me. But 100 good form pushups or 20 pullups(or 10 weighted) impresses the hell out of me