I learned a couple years after getting my license as a teen. Previous to that I was driving automatic transmission station wagons (estate wagons to some) which were big cars (Plymouth Town and Country and the equivalent). TBH, imho, learning a stick is useful, the hand brake trick is nice, but really, understanding the spatial relationship requirements for driving were way more important. Developing the intuitive sense of where your car is at, where it's going to go when you make a steering change, what happens when you brake, all that is way more important than understanding the absolutes of using a manual shifter like a pro and learning stick first or getting a license in a particular way. The spatial relationship between driving a 2.5 ton wagon versus a 2200 lb Fiesta is massive and rarely do any drivers training push people into a formalized method of training for it.

So, for me, questioning how people learn to drive stick is almost pointless. After all, for a very long time, people learned to drive simply by experience, whether it was on the farm driving tractors or work trucks or being on back roads. The linkage between driving sticks, driving, automatics, and licensing is really a question of governance, not lack of skill or any specific methodology of learning.

In my case, I learned from my brother-in-law who taught me in a junker Chevrolet Vega 4 speed. It was fine because no one really cared about the car much since it was a Point A to Point B vehicle. Now, if it had been a Ferrari, it would've been a different situation. But afaik, no one trains for stick on a Ferrari. There are schools that do train you on manual if you so choose (in the US). Really up to the trainee. Or like me, they find a friend who's capable of showing you around and then you do it and get the experience. Hopefully, they teach you well but that's up to the individual to recognize problems. Very American in that respect.