If we look back in history, why has the role of creating money fallen to central banks?

What will be an ideal response?

Historically central bank money has been seen as more trustworthy than the money issued by emperors, kings or queens. Often times rulers would have a strong incentive to default on their notes (debts) rendering the currencies they issued as worthless. Early central banks on the other hand, kept adequate reserves (usually gold) to redeem their notes.