Tell me where I'm wrong.
Your wish is my command!
First, you need to understand that it is not just the banks that are the problem; the reason banks exist is that they have customers who need their services. In order to match reality, we have to add another piece to your analogy: suppose that you have to pay $2,000 in rent at the start of the month, but don't get paid until the end. You don't have a solvency problem - you are paying your debts completely on a monthly basis, just using credit to time-shift your cashflows. But when that credit is taken away, you are thrown out on the street.
In this case, of course, you would just keep a few months rent on hand to solve the problem. But that is not how businesses function; their cash requirements are vastly greater as a fraction of their capital than yours are. A company that has an order for widgets at $1.01 may be quite profitable if the cost of production is $1.00 provided that they don't have to fund production before delivery. They are still using credit to manage their cashflows, but it would be extremely expensive to dispense with this credit by the solution of keeping the requisite cash on hand. So expensive that they would be put out of business by more efficient competitors. The trouble now is that it has become very expensive or impossible for non-bank corporations to use credit in this way.
Neutrinos have bad breadth.
