While people have erroneously compared it to "interest on loans" in their attempts to understand all this, that's categorically not what's happening in Lightning. "Loans" and "interest" imply fractional reserve and there's none of that in LN. If that's the impression you were left with, perhaps it's you who needs to take another look at the whitepaper.
fractional reserve banking stopped working years ago with main stream banks and they no longer need money on deposit to print new notes but your argument is like
saying that because a street light is left on at night that it's not night time because you can see in the dark.
Interest + fees = Banks and not only is this centralized in the case of hub-banks going down but it is also off-chain so may I suggest that perhaps you
need to read the white paper again instead of letting them pull the wool over your eyes.
A Funding Transaction may have multiple outputs with multiple Commitment
Transactions, with the Funding Transaction key and some Commitment
Transactions keys stored offline. It is possible to create an equivalent
of a Checking Account and Savings Account by moving funds between
outputs from a Funding Transaction, with the Savings Account stored
offline and requiring additional signatures from security services.
It stinks of banks, face up to the facts.