If my son swallowed something or there were some other such emergency, it would be irresponsible to waste time driving home to take him to the ER - that's what ambulances are for. They could have him in the ER and taken care of before I could get back home from work no matter how fast I drove.

Besides, if a spouse is home with the kid, why would *I* drive him in - she's there and has the car.

Also it depends on where you live. I have a friend who works at a hospital and lives close-by. The ER is 4 minutes away by bicycle, and about 20 minutes by car, due to being able to cut through the woods on the bike, but on the car having to drive several miles around the woods, park in the parking structure then walk several hundred meters to the buildings.