Only because they are.
banks operate on fractional reserves.
Yes.
Fractional-reserve banking is the practice whereby a bank accepts deposits, makes loans or investments, but is only required to hold reserves equal to a fraction of its deposit liabilities.[1] Reserves are held as currency in the bank, or as balances in the bank's accounts at the central bank. Fractional-reserve banking is the current form of banking practiced in most countries worldwide.[2]
banks must keep that fraction of their outstanding loans in reserve.
No. They reserve a portion of deposits, not a portion of their loans.