Why the Kido Butai did not bring every carrier to Pearl Harbor

Why did the Kido Butai use six carriers at Pearl Harbor rather than every available Japanese carrier?

Many other carriers lacked readiness, aircraft, pilots, or tanker support, while the six-carrier force already stretched available resources.

The six-carrier force already represented nearly everything Japan could make ready and support for the operation. Additional carriers required trained air groups, aircraft, readiness, and tanker support for the voyage. Logistics and trained personnel constrained the striking force even when more hulls existed on paper.