Why, then is this learning to fly in the circuit still going on?
I really don't know,
I find circuits boring as hell and a right pain and made it my mission to spend as little time doing them as possible.
Every single student I inherited who was having problems lacked the basic handling skills. In every case they had only spent less than an hour on S&L I/II and Effects of controls. Every single one of them was taken away from the circuit and those lessons revised. Then they usually got an hour of trimming and flying attitudes for different configurations which to be honest is equally boring for me but is more than worth it.
Then I got them flying the correct speeds.
And usually that was enough for another 1-2 hours doing circuits and then off solo. Which to be honest the majority of my own students used to do.
Its all in those first lessons which some seem to skip.
I know I shouldn't but with my day job line training I quite often have to do the same lessons on S&L and trimming for different configurations for new multicrew pilots. As they "get it" their work load drops off and then they improve leaps and bounds.