Why rev-match before a turn instead of just shifting after?

I've been wondering about the whole rev-matching and downshifting process when driving, especially when taking corners or driving in the city.

Why do people recommend downshifting through the gears before a turn (like going from fourth to third to second) instead of just staying in fourth, taking the turn, and then shifting directly to second after exiting?

To me, it seems like the second method is more efficient—you brake, turn, and shift after. The first method requires braking, downshifting multiple times, rev-matching, and generally doing more steps. Wouldn’t it be better to just trail brake into the corner, then shift while braking or even after the turn?

Is there a real advantage to doing it the traditional way? Or is it just something people do out of habit?

Would love to hear some opinions from experienced drivers!