More involvement per player
In five-on-five, a young player can spend long stretches without touching the ball or making a meaningful decision. Smaller games increase involvement.
More involvement does not automatically mean better learning, but it gives coaches more opportunities to observe and players more opportunities to act.
The reads become easier to see
Removing some players reduces the amount of information without removing the essential basketball problem. A two-on-two can make help defence, spacing and timing easier to notice.
This allows the coach to simplify the picture while keeping the decision real.
Skills gain context
A crossover in isolation is different from a crossover used because a defender takes away the first lane. A pass becomes meaningful when a teammate's movement and a defender's position create the window.
Small-sided games let technical work return quickly to the environment where it has to function.
Competition can stay purposeful
Score, time, space and rules can create pressure without turning every exercise into a full game. Coaches can adjust constraints to emphasise a development theme.
The objective is not to make practice complicated. It is to create enough realism that players must see, decide and adapt.