Why don't we have a full reserve banking system?

A full reserve banking system is not widely adopted primarily due to concerns about economic efficiency and credit availability. In such a system, banks are required to keep all deposits in reserve, which limits their ability to lend money and can hinder economic growth. Additionally, existing fractional reserve banking allows for greater flexibility in managing liquidity and facilitating borrowing, which is crucial for stimulating investment and consumer spending. Political and institutional inertia also plays a role, as the current banking system is deeply entrenched and supported by established financial practices.