Another important difference between the classic physique and the "Hulk"-like physique is in the development of the traps and the appearance of shoulder width. In the chemically-enhanced, cartoonish "Hulk"-like physique (remember the "Hulk" was a cartoon/comic before they made it into a TV series and film), the traps are almost always vastly overdeveloped compared to the classic physique.
The problem with overdeveloped traps is that they make the shoulders appear more "rounded" and narrow rather than square and broad. One of the hallmarks of the classic physique is broad shoulders. So to enhance the appearance of broad shoulders, classic physique builders would intentionally not overdevelop the traps. In some instances, upper traps would not have to be exercised at all.
In his book, Building the Classic Physique The Natural Way (p. 70), Steve Reeves explains "Don't misunderstand me, the trapezius is a good muscle to develop - for supreme strength. If you're a competitive weightlifter or powerlifter, then you need that trapezius development to generate the extreme power required to make heavy lifts. But if your goal is to have a good physique, and be strong (if not necessarily the world champion in a strength sport), then you don't need that extra development in the trapezius."
Take a look at the photos above (left: Steve Reeves - Mr Universe 1950, right: Ronnie Coleman - Mr Olympia 1998-2005) and judge for yourself. Whose physique looks as if the shoulders are broader? Whose physique would you rather have?