Because they are over-driving the car. Not because driving a car is difficult. Also, there are adverse conditions involved, where they shouldn't have been driving in the first place.
I've been posting a long wall of text, but seems I've missed my initial point.
Even before we consider forces, weight transfer, road imperfections - I assume if someone would give McLaren P1 to you, me, apex911 or whoever else who haven't experienced such cars before, and ask to drive 30 mph round the bend, we would crash it. IF we approach it like we approach our sim cars: not learning the throttle/steering response, overall dimensions of the car, and turning off everything that's possible to turn off because we're the hardcore men.
Also the argument of "can't drive 30 kmh around the bend in /name your preferred simulation/" lacks the details, like what you've been doing before your car reached 30 kmh and the bend. Where the car was in relation to racing line, was it accelerating or braking, if braking - how, had the weight of the car been put at least a little to the centre while entering the bend, or was it all at the front in the moment of turning. Was the bend cambered? How abbrasive the surface of that bend? Etc etc. If we're talking about skidpad, well the same - what forces were applied and when. Also one thing I believe goes misconceptioned about skidpads is that in reality they are not perfectly flat, while in simulations on some test tracks they don't have even 1mm difference. Making a slight physical noise to the skidpad would lead to more realistic, even if very subtle to notice, behaviour.
But what is simcade?
hell even a Kart and try to see what grip is and what feel is...
Funny you mentioned that, because the kart is one of the easiest examples of how the illusion of infinite grip can bite you in the, uhm, rear end.
The lack of suspension and very short wheelbase makes it react to slightest difference instantly. While the chassis flex can help you in some situations, in others it will make you confused, as well as lack of front brakes; and rear brakes that can make the kart both understeer and oversteer.
CARS GRIP!!!!!!!!!!!!!!!!!!!!!!!!
Define what is a car to you.
To me, car is a sum of it's parts. And cars don't grip. Tires do grip. Cars do both - help tires grip and get in the tire's way to grip, depending on the speed, conditions, and type of car's component specs (aerodynamics, suspension, weight and weight distribution, etc), former and latter may vary.
When I had my previouos car, I've been taking it to the track with different tires. One set of tires was more "loosy", the limit of lateral grip was lower, but it was more linear and progressive as well. After you sense the lateral grip is lost, it's easy regained.
Then I went to another tires later on, and their limit of grip was way above the previous tires. The car behaved like a different car. But when that limit of grip is reached - it's done. It was never been able to regain until the car is backwards, or until you have time/space and actually engine momentum to power through and get the car drag itself from the slide (it was FWD). There is a corner where you're meant to trail brake, but also when it starts it goes downstairs. Using former set of tires, I've learned where the limit is, and it was not such a big deal, the grip was quite easily regained. Using latter set of tires the car set itself backwards within a second. Other components of the car were the same, and the time between runs was short, so nothing became too much worn out to make such difference. Only tires. Even season/time of day were the same.