I believe Zhuge Liang's Northern Expeditions were a political tool for military posturing.

He approached the first Northern Expedition with sincerity,
but even that ended in failure due to poor management of his troops.
After that, it felt almost meaningless; it felt like he was using the expeditions as a tool to consolidate his own power by diverting internal dissatisfaction caused by being overly cautious.
He would follow predictable paths, engage in a standoff, and then simply retreat.
It was basically a joke.
Without the Northern Expeditions, Zhuge Liang's power within Shu Han would have been absolute, and given the extremely rugged terrain, I believe the internal power structure could have been destabilized.