As far as the drive to increase muscle size goes, there are a couple of good reasons to do it.
Increased size/weight is increased leverage (moving more external weight, rather than bodyweight). This is the point made with the linebacker earlier. But increased muscle size is also protective, especially in high contact sports. More "under armour" means less likely hood of getting injured, so big shoulders and back muscles can be very beneficial.
More size also correlates with greater strength potential, to a point. Bodybuilder style training can actually affect the alignment of muscle fibers, leading to increased efficiency of force production. They might not have the edge when it comes to maximal force production, but they have a fairly high level of strength endurance.
Chasing size to the detriment of health, that I will never understand. But if your goal is to be able to pick up anything, or avoid injury, or just to intimidate the people around you, then increased size has its purpose.