I think most of the time is due to the really fast drivers having insane levels of skill (Aliens) in the positioning of the car, turning perfectly, getting perfect traction and braking on the limit.
I agree with what you're saying, and I have no idea of whether I'll ever be as fast as the aliens, but considering how bad my brakes are{and who knows how dodgy the accelerator pedal is}, IMO, I should find plenty of time at say Imola where there's 14 corners, so each time I have to hit the brakes, now I'll have a better brake bias/pressure, and the car should stay online.....think of the lost time having your brakes lock up, and then either deal with the overrun, or the transfer of energy thru the car when you have to come off sharper than you otherwise would.
If it turns out I'm no faster with the CSP's, then at least I know I've more work to do, or just don't have the magic eye, but I hate being slower and believing it's the equipment.....so for the relatively small amount I might spend, it'll be worth it, at least to me.