Why the IJN built dedicated training ships

Why did the Imperial Japanese Navy use purpose-built training ships?

They were useful training platforms and offered naval-standard hulls that could be adapted for other roles.

Dedicated ships provide a stable platform for training without consuming frontline combatants. Their spaces and routines can be organized around instruction rather than an operational deployment cycle. Because the hulls are built to naval standards, they also retain more military utility than converted civilian accommodation alone. Wartime pressure can therefore turn them toward auxiliary roles after the training establishment has extracted value from them in peace.