It's actually Pretty Bloody Hard(tm) to store or move money/wealth safely and properly, not the least because most of us are all highwaymen when given the opportunity. Banks exist to try and bring some civility to that madness, with the cost being (ideally) a pittance skimmed from the top to keep their highwaymen tendencies at bay.

If you want to call them a protection racket akin to the mafia... you're probably right.

Of course, banks these days are much more than that and there's plenty to rightfully crucify them for. But even still, there's a reason being called a third-rate bank clerk is an insult among the highest order.