Most Helpful Guy
The trouble with jocks is that there is no measurement for cup size. It is supposed to be one-size-fits-all. Imagine women's bras were one-size-fits-all! That would be insane.
Now imagine what happens if a man with D-cup gonads wears briefs with A-cup sizing. In order to accommodate his manly hood, the powerful leg elastic gets stretched away from the leg, and all that tension crushes his gonads. Men in this unfortunate situation have no choice but to either have their underwear tailored, or just go free-balling with boxers, which have their drawbacks too.
My perfect underwear would be briefs with about 12cm of material between the bands of leg elastic. They just don't make them like this.