Because it is often kept apart from the ledger — a spreadsheet per account. Two records of the same money drift, and by close neither can be trusted without checking the other.
The cash book records every receipt and payment through each bank or cash account, in date order, with its running balance and its ledger posting.
It is a view of the ledger's bank accounts rather than a second book. Every line is a posting, reconciliation status sits on the line, and the balance always ties.
The balance is out by an amount nobody recognises. Filtering to unreconciled lines shows a payment entered by hand and also picked up by the feed — one reversal and it ties.
It does not cover money that never touched a bank account. Contra settlements and journal-only movements live in the ledger, not here.
It ties to bank reconciliation, the general ledger bank accounts and cash flow actuals, per entity and per account.
Yes, reconciled by count rather than by statement.
Yes, per entity and per account, or consolidated.
Yes, both balances are shown.
Fourteen days, every module, no card. Or half an hour with someone who will run it on your own records and tell you where it does not help.