Why the swimbriefs has a small lining inside the front?

[7_of_Fine]

I might make the case that the liner helps keep the "structure" of the pouch intact longer, so your bulge doesn't hang between your thighs any faster than it has to. :P

none of my suits have liners, whether they originally had one or not. If I'm going swimming in public, I have a nice swim jock to act as such a lining.