Honestly doctors can spread a lot of disinformation on things not biologically related. For example, our pediatrician recommended we wait until 3 to potty train our son... who at the time was already potty trained.
Potty training is also something that differs widely between developed nations and rest of world.
Some medical professionals also spread incorrect information regarding medical information. For example, an RN gave us incorrect info regarding something she claimed was necessary and was CDC-recommended. We asked for more information, and lo and behold, the CDC specifically said it was not necessary (and there were no other sources recommending it).
Doctors and their staff have an incentive to perform more procedures/tests because they get paid to do so. Because the patient often does not bear the full cost of procedures/testing, patients often do not do much diligence to see whether these are actually appropriate. While I don't think that the RN we were talking with was being malicious (surely her individual comp would not have been affected), I do think this is a symptom of a system with a principal-agent problem.
Of course, doctors can be an incredible source of information. But with all things, consider any potential conflicts of interest when taking advice.
> Potty training is also something that differs widely between developed nations and rest of world.
And between kids. My daughter just up and decided at around 18 months or so that she was done with diapers and would use the big girl potty. Not one accident. My son was more apathetic about the whole thing, and it was sometime past his third birthday before he finally started using the toilet to poop in.
The piece of advice that stuck with me ... don't bother trying, they'll do it themselves when they're ready, and you probably can't accelerate it.
What you're saying goes to the heart of the article: Why are things so different in western nations compared to developing nations w.r.t. child raising? Potty training is one of the many places where we diverge wildly.
Take for example Vietnam, where kids are out of diapers at around 9 months[1]. Even in the US the age at which children are potty trained has crept up slowly from 1 year to 19 months to 27 months today:
> In the U.S., until the 1950s, most children were using the potty in the first few months of life and completely trained by age 1. In the 1970s, 18 months was an average age to start. Now, it's around 24 to 30 months.[2]
As the article asks, what are the phenomena causing these changes and what explains the huge discrepancies between countries and cultures? Clearly the biology of children does NOT explain the difference.
Diapers are cheaper, and disposable diapers more widely available. That could potentially shift the scales for what is more difficult (hand washing diapers vs training at a young age whereas now: disposable diapers and wait until training is easier)
I think that has to do with the fact that not all children are able to learn/sense it at a young age. Telling parents their kids should be potty trained before the age of 3 could have the parent put pressure on the kid resulting in worse behaviour or aversion to using the toilet, lengthening the process even further. It's just easier to advice to "start at 3". Especially since nowadays more parents both work fulltime and will have less time to properly observe and guide the process at earlier age.
Potty training is also something that differs widely between developed nations and rest of world.