He's a young dark haired boy with Superman's powers, wearing red, blue, and a cape, and the S shield plastered on his chest, and he's called Superboy. If a casual reader passes this comic by on the stand and sees that, they at the very least know the deal on a conceptual level: this is related to the widely known (Superman's notoriety is inarguable, obviously) Superman character. Superman's S is a literal brand recognized world wide. The next question is "whoa, ok, who's that kid?" and the answer is--and here's the beauty of it all--"he's Superman's son." Three simple words with all of the gravity in the world.
Hell, he's even named after Superman's dad, so if you have even a passing familiarity with the brand it'll be easy to remember. DC created Jon for marketability. I remember Jugens saying in an interview that he came to DC with the rough idea for a son for Superman, and DC gave him the name and the rest. They knew damn well what they were doing. Even if your casual passer-by doesn't know much (or anything) else outside of Superman related TV and movies, Jon, no matter his form, is completely accommodating of the strength of his super simple concept. No eyes glazing over at wiki entries while just trying to understand what he is. Jon is Superman's son. That is the beginning middle and end of it of the entry point into the character.
The kid's recognizablity is inbuilt even if the perspective fan doesn't know it yet. Jon is the definition of overt marketing in mainstream comics.