Might be that the stabilizing muscles are weak or just not as strong as rest, the plank really helps. Or it just might be that the only real solution is cosmetic surgery (it's rare that it's the only option) but some guys have to through it to get to the level they want.
Dont scare me by saying cosmetic surgery I didn't used to be like this the first year of training i had a flat stomach. I find it hard to believe a plank could make such a difference tho. Could it be that im just fat there? it so strange its like constant bloat surely if its fat i would not be able to see my abs? Help lol