I’m pretty sure most sims setup things like this or with similar concept as it makes it simpler to handle forces: you have to calculate the related forces around the chassis anyway. That being said, I seriously doubt those wheels are actually using rigidbody to rigidbody collisions for ground contact in any of them. Even if generic physics engine had soft body physics support, I wouldn’t count you could use it for tire modeling purposes as it’s a very complicated subject.
If you don’t want/need to model proper tire flex, you’ll still have issues to solve with rigidbody contact and collisions. If you just have a rigidbody against another rigidbody, it can bounce on top of the surface. That’s also the reason it will start acting weird when you get to higher speeds/uneven surfaces and either collision responses overshoot or wheels suddenly loses contact when you’d expect it to be on ground (you wouldn’t want to drive 200km/h with a car equipped with rigid cartwheels in real life either).