Why do Americans not back into parking spaces?
The real answer is: I don't know. But I've collected some interesting facts about this behaviour.
Global Variation
There appears to be a wide variation between countries regarding back-in parking. A fun paper was published by Professor Shoamin Li titled, "Predicting Productivity Gains from Parking Behavior." (Reference link at bottom of page)
When he was visiting Taiwan, he noticed that his hosts went far out of their way to find a parking space that they could carefully back into. He wasn't sure if this behaviour was unique to his hosts or more gemeral. So he did a small study where his friends in Brazil, China, India, Russia, Taiwan, and the USA sent him photos of everyday parking garages and lots at department stores and supermarkets. He then analyzed the photos to look at how many cars had back-in parked.
The results of his study are pictured below. In the USA only 6% of the cars studied were backed in. In Brazil 17%, India 25%, Russsia 35%, Taiwan 60%, and in China 88%.
His study then proceeded to hypothesize that Asian values of delayed gratification were an explanatory factor of not only why people in certain countries back-in their cars in more, but also how their increased economic growth and productivity correlated closley with the number of backed-in cars. You can evaluate for yourself the value of this claim.
In short, in countries outside of the USA it is more common to back in.
Update April 12, 2021
From Reddit:
Australia: "In Australia most big workplaces make you reverse park because it makes evacuation smoother in case of emergency. So it might just be a health & safety thing there too."
Japan: "Almost everyone in Kapan reverse parks"
Why don't we back into parking spaces?
When speaking with my friends, many agree it makes more sense to back-in. The previous two blog articles go into great detail regarding the huge number of deaths and injuries from backover accidents and the safety benefits of backing in. Tom & Ray from Car Talk agree we should back-into parking spaces too; so this must settle the matter.
However, my friends most often tell me that back-in parking is "harder" and that they are "not good at it'. This makes sense to me, and I believe is a primary reason that we don't back-in park in America. It's not something routinely done, and therefore we're all not that great at it.
Fortunately, this is something that practice in an empty parking lot can fix.
Furthermore, new backup cameras overlay the screen with lines to show where the car will fit, which make it even easier.
When I was taking my driver's test in high-school, it was mandatory that we learn to parallel park. Many people found this a harder part of training. However, people practiced and clearly could do it (at one point in their life) because parallel parking was a mandatory part of the driver's licensing test. Perhaps back-in parking should also be added.
UPDATE April 22, 2021. I am informed that in British Columbia, "reverse stall parking" is a required manoeuvre that driving students are taught and may be examined on.
Other reasons back-in parking is not preferred
Reading the online message forums, it seems that back into parking spaces is illegal in some United States jurisdictions. One hypothesis is that Automated License Plate Recognition (ALPR) cameras would not work. These cameras scan the license plates of cars as they drive by them to ensure the car has paid to park there. Many jurisdictions do not require front-bumper licences plates. Therefore, cars that had back-in parked wouldn't be displaying a license plate on their front bumper to be scanned.
Others suspect that the reason some lots don't permit back-in parking is that drivers may accidentally bump into the building if they back in. Or perhaps if the car is idled, its exhaust will leave smoke damage against the wall.
Another suggestion was that if a dining patio or sidewalk is at the edge of the parking lot. If cars backed into those spots, the exhaust from the cars would pollute the patio or sidewalk.
Someone who used to work at a sporting event parking lot suggested that they forbid back-in parking because it made filling the lot slower.
Conclusion
Whatever the reason, one thing is clear. There are too many accidents from backovers, and turning the car around to pull out forwards is an intuitive way to reduce this risk. In many countries outside of the USA, back-in parking is more prevalent, and in some, even the norm. We can all spend a bit of time in an empty parking lot improving this skill, and with effort, turn our parking lots around.
References
Predicting Productivity Gains from Parking Behavior
https://www.researchgate.net/publication/263658306_Predicting_Productivity_Gains_from_Parking_Behavior
https://www.quora.com/Why-do-they-not-want-cars-and-trucks-to-back-in-in-an-open-parking-lot
Vox: It’s much safer to back into parking spaces. Why don’t we do it?
https://www.vox.com/2016/8/1/11926596/safer-back-into-parking-spaces
Reddit: "Almost everyone in Japan reverse parks"
https://www.reddit.com/r/mildlyinteresting/comments/6zl2e3/almost_everyone_in_japan_reverse_parks/