Until 1998 doctors considered choline an accessory nutrient. It was deemed non-essential because it can be made from the essential nutrient methionine.
But then a bright spark had an idea: maybe choline is still necessary because on average we cannot make ENOUGH choline to adequately meet all of our needs.
All that time, virtually no one would have been deficient in choline but for the advice of idiot doctors: stop eating eggs (because of the fat and cholesterol) and start eating heavily fortified, highly processed grain products, AKA breakfast cereals.
Egg yolks are loaded with the essential nutrient choline. A delicious three egg omelet can supply all we need, but who was eating them? Very few, thanks to doctors.