> Or does bookkeeping for some weird reasons really record each amount twice?
There is a surprisingly common reason, but it isn't weird. Consider a paycheck. You have income, but then you split that up. Some pays for insurance premiums, some is withheld for taxes, some may be contributed to a retirement account, and some is deposited into a bank account. Earnings is a credit to an income account, but everything else is a debit to some other account. The total debits equal the total credits, but each credit and debit must necessarily be a separate entry, because they all affect different accounts.
In essence you are just recording transactions with source and destination accounts and the amount. And at least in principle you could just log all transactions in this way without any redundant information. If you insist on making the change to each account more obvious, then you will have to record the amount twice, once for each account, but if you are doing the accounting with a computer, then I would guess that you always just record the transaction and only show the amount twice with different signs for the two involved accounts. Or does bookkeeping for some weird reasons really record each amount twice?