This unrealistically high grip expectation has been a part of "racing" games for so long, most don't want to believe how much grip cars actually have (or dont have) in high performance situations. I have guys I've done track days with that tell me I'm dumb to drive on comfort mediums or softs on GT5. "That's unrealistic!" they say.
It comes down to years of arcade video game conditioning and a lack of tactile feel. We must rely on vision and audio alone to get a sense of speed. FFB through the wheel alone is not enough. Watch a few raw interior, forward facing videos of road car on a track. It usually looks and sounds like the car is tip-toeing around, even if the guy behind the wheel is giving it the beans. Compound this with the expectation of Hollywood-chase-scene action all to create a false sense of what tearing around a track should feel like.
Comforts for road cars (in general)
Racing Med or Soft to win unwinnable races
Everything in between for highly modified cars/racecars