If you're a small organization with minimal or straightforward income from CiviCRM, you probably are happy with using CiviCRM income reporting for the purpose it was originally designed, i.e. for helping you engage with your constituents.
But if you are larger, use a payment processor, and your reporting needs are more complex (especially political parties that need to report income rather carefully), then you will have run into the challenge of reconciling payment processor income in CiviCRM against your bookkeeping system and/or your bank account.