I disagree and I think it has everything to do with RPM;
One cylinder of a 2ltr car engine = 0.5ltr capacity per cylinder per stroke.
Once cylinder of a 1ltr bike engine = 0.25ltr capacity per cylinder per stroke.
The cylinder draws air every other revolution.
At 6000 RPM (typical car engine red line), one cylinder on the 2ltr engine would be drawing 1500 ltrs of air per minute through the carb barrel.
At 13000 RPM (red line figure of a cbr1000), one cylinder on the 1ltr engine would be drawing 1625 ltrs of air per minute through the carb barrel.
So by my understanding, bike carbs are able to handle the mass air flow rate that a car would put them under.
Fuelling on the other hand - for every intake stroke, whilst the bike carb can provide enough air as calc'd above, the car engine would also need more fuel due to it's larger cylinder capacity (for every suck, it can get all the air it needs but not enough fuel), which to me explains the reason why the jets on bike carb need adjusting / enlarging to suit a car applications.
Lets face it, if people didn't get acceptable results from bike carbs, they would be as common on car engines as they are currently.