If they're really, really good.

Here in Munich, our public transport is much better than any American city, but I still hate taking the train in summer. AC either does not exist or is far too weak. Taking the car takes 40, maybe 50 minutes, the train 1h25min. I still take the train, mind you, but it's so much more exhausting than the car...

I have to mention my daily commute is between two cities outside Munich.