Piloting an aircraft and driving a car is not the same thing, at all.
Correct. There is far more likelihood of injury, death and damage to multiple third parties and property when driving a car and suffering medical incapacitation than when flying, and yet no medical is required for driving.
I see no significant statistical justification for PPL medicals, amply demonstrated by the complete absence of any medically related aviation fatalities involving NPPL holders "flying on a car licence"
The most effective medical is a perfectly natural sense of self preservation.