Why does cash reserves typically account for a small proportion of a bank's assets? A bank makes higher returns by holding more liquid assets such as loans. It is expensive to keep too much cash in highly secured vaults. Cash reserves are very liquid, and it is risky for banks to have too much liquidity. Cash reserves are held in vaults and therefore not electronically transferrable between banks. A bank makes higher returns by holding riskier assets such as loans.

The text you provided is in English, so I'll continue in English.

Cash reserves typically account for a small proportion of a bank's assets for several reasons:

1. Higher Returns: Banks can make higher returns by holding more liquid assets such as loans. Loans generate interest income, which is a significant source of revenue for banks.

2. Cost: It is expensive to keep too much cash in highly secured vaults. Banks need to pay for the security and maintenance of these vaults, which can be costly.

3. Risk: Cash reserves are very liquid, and it is risky for banks to have too much liquidity. If a bank has too much cash, it may not be able to invest it effectively to generate returns.

4. Transferability: Cash reserves are held in vaults and therefore not electronically transferrable between banks. This can limit a bank's ability to quickly move funds where they are needed.

5. Riskier Assets: A bank makes higher returns by holding riskier assets such as loans. While these assets come with more risk, they also offer the potential for higher returns. This is why banks often prefer to hold these types of assets instead of cash reserves.