Football is a hip driven sport. Period. Blocking power comes from the hips, hitting comes from the hips. Explosiveness comes from the hips. Have you ever tried pushing somebody without using your legs? Or better yet, pushing somebody while sitting down? Well, you don't get much power. When you push/block somebody as hard as you can, the majority of that power comes from the lower body.
Bench press is a nice measure of upper body strength, and thats it. Training to your sports specific movements are key in S&C. Which is why squats and cleans are important. Squatting develops your hips, glutes, hamstrings (when done correctly). All important for lower body power. Cleans develop your body's triple extension, which is used in running, jumping, and explosiveness. When in football are you laying on your back pushing something off your chest? Never, unless you are on the bottom of a pile pushing people off you, or you just got laid out, are face down and need to push yourself back up. Yes, bench press is kind of important in overall upper body strength, needed to give your opponent that pop in the chest. But, the vast majority of that "pop" comes from the lower extremities.
The reason bench press is a widely used testing factor for upper body strength is because its very easy to rep out a high number of reps, without the risk of injury. It's also a lift everybody can do, relatively easily. If the combine tested athletes on how many reps they can squat, clean, or deadlift at a given weight, you would see numerous lower back injuries, because once you start getting fatigued your form goes to crap and you start lifting with your lower back. While on the bench press, once you get fatigued you can't really hurt yourself, you just can't do anymore.
