I think it is incorrect to say that bodybuilders, especially NPC/Professional level, are not strong. It depends on what context you use to measure them. They seem to always be compared to power lifters/Olympic lifters.
I remember watching one of Jay's videos. It was the one where he lost to Coleman for the last time. He was benching 315, very strict, for around 8 or 9 reps as I remember. He was squatting 405 for maybe 10 reps or so. Now compared to hard core lifters and when you look at the size of Jay it doesn't seem like much. But when you compare him to athletes from other sports, forget the average gym rat or person on the street, he is incredibly strong. Even many juiced up football players and wrestlers his size will find it hard to match that performance.
Bodybuilders are not strength athletes as such, but as a group they are certainly one of the strongest people on this planet. Even the average gym rat is far stronger than the average fatty waddling around in this country. Personally, I am below average strength wise when I consider how long I've been training and how I match up with others in the gym. And I always strive to lift as heavy as I can using strict form. If I can get 12 clean reps on an upper body exercise I will increase the weight and I almost always try to exceed my previous performance. If I did 8 reps the last time I think 9 reps this time. But despite the fact that I am considered pathetically weak in the gym in normal everyday life I am considered strong and I'm always the one at work that gets asked to move the fucking boxes of computer paper or other crap that needs to get moved or lifted.