lawful money cheque can not be held as reserves for the bank.
so they can't fractionally lend it out, making their credit pool and reserve much smaller and the law states they need a certain amount in holdings.
took me five days once to take out a large amount of cash from the bank and it was in the account.
called them monday and it was there on friday.

i was trying to change dollars into peso's once in mexico and the man in front of me deposited a pile of peso's.
i was next inline and the bank told me they couldn't because they had no money. i said what about that pile of peso's that man just deposited? she said it wasn't theirs.