> And besides that, banks need capital reserves in the form of customer deposits

USA's fractional reserve requirement is now 0%. UK has also gotten rid of their reserve requirement as well. In the UK, the limit to what the bank can loan out is more determined by the market cap of the bank (committed shareholder value). Cash is only strictly needed to cover ... customer deposits.

So in the UK, if a bank gets rid of customer deposits entirely, then it kind of doesn't need any cash anymore. It can just lend money out of thin air based on its total net worth (market cap).

> Retail banking in general makes boatloads of money, and deposits are central to this now that we're out of zero-interest-rate-land.

Talking about banking in general is generally a huge mistake. While deposits may be central, retail deposits are irrelevant for the banks that do > 70% of banking.

> now that we're out of zero-interest-rate-land.

Doesn't matter to them.

Banks get their reserves by borrowing from the Fed or from other banks that may have deposits. The idea that banks get reserves from deposits is severely outdated. Deposits are free reserves to the bank, but the overhead of maintaining customer accounts makes them an unattractive option.