3rd person view is horrible. You really can't play seriously this way as you cannot judge how to get the correct lines etc.
I would imagine 3rd person view appeals to less than 10-year old children only.
Wow. So it's impossible to "judge how to get the correct lines" when you have the best possible view of upcoming corners, an improved sense of speed (everything looks faster), no drop in visibility in wet conditions, and know exactly where the extremeties of your car are at all times?
First off, I tend to use the interior view in games, or the bumper cam when an interior view is unavailable; not only is it more intuitive and immersive for me, but exterior cams are usually quite awful to play with, particularly as the physics engine leans toward the side of "realism." If the camera is too "rigid" or too "loose," it can throw everything off. However, I found myself using the exterior cam almost exclusively in GT5, at least in any race that was halfway challenging. I still used the cockpit view when driving casually, facing braindead AI in a "normal" race, or racing online.
The main motivations for me to use the exterior cam were the framerate and sense of speed; it was the
only view that didn't run into FPS hiccups, which I thought was odd. Even the bumper cam in standard cars (with no weather effects or other cars on-screen) caused problems! Using the exterior cam ensured ideal visibility in all conditions, made judging braking distances (ie. how fast I was going)
much easier to do, and helped me slip between AI cars in the "Overtake" license tests. As a bonus, I got to appreciate the well-modeled premium cars while I drove them, beyond the sometimes-claustrophobic interiors.
Call me a 10-year-old child I guess, but GT is unusual for a "sim" in that the exterior cam is not only usable, but helpful. I'm a bit like you in that I can't understand why people would want to use the exterior view in certain racing games; some just have disorienting camera control. But there's no reason to assume it could only appeal to children and bad drivers.