It’s been a while since I took a monetary theory class, but if people are interested in your first point they should look into fractional-reserve banking.
Essentially banks are only required to have a fraction of their deposit liabilities as liquid assets and can loan out the rest. If I remember correctly, this is actually how a substantial amount of money is created in the US and likely most of the world. If you deposit $100, a bank could make a $1000 loan assuming the reserve rate is 10%, which leads to an increase in the money supply of $900.
Money supply is definitely not the same as the size of the economy, but it is incorrect to say that bank deposits are just sitting stagnant. Banks are quite active with those deposits - how else would bankers make all that money!
Bankers make money by creating loans, which are subject to regulatory requirements imposed largely through the adoption of Basel III. The reason they take deposits is because they are the cheapest form of liquidity. The certainly don't make money lending out deposits, whatever that means. Many countries don't even have reserve requirements, which rather highlights the flaw in the fractional reserve model.
I don't think you know what 'liquidity' means, but if you do you are incorrect about it here. Deposits provide funding, not liquidity. Banks certainly do use deposits to fund loans.
It is not true that most countries do not have reserve requirements.
I think before commenting further you need to take a deep dive into actual banking operations, because you really are wide of the mark. I posted a few links in the other post local to this one that might help. I also suggest reading the Basel III accords (or at least a summary) to understand the role of liquidity in banking.
There's not much point me discussing this further with your since you're so wrong. Take care and good luck with your enquiries.
I do think that your original argument that bank deposits don’t contribute to economic growth is wrong though. As you point out, they are a cheap form of liquidity for lenders. I think you’d agree that loans play a key role in economic growth.
The ability of banks to lend is limited by the availability of credit worthy borrowers, not liquidity. Banks will always get the necessary liquidity from the central bank (assuming the system is working as intended), but prefer deposits because they are cheaper than whatever is offered by the CB. Inter-bank lending is an alternative preferred option if insufficient deposits are available.
Essentially banks are only required to have a fraction of their deposit liabilities as liquid assets and can loan out the rest. If I remember correctly, this is actually how a substantial amount of money is created in the US and likely most of the world. If you deposit $100, a bank could make a $1000 loan assuming the reserve rate is 10%, which leads to an increase in the money supply of $900.
Money supply is definitely not the same as the size of the economy, but it is incorrect to say that bank deposits are just sitting stagnant. Banks are quite active with those deposits - how else would bankers make all that money!