The instinct is to protect accuracy by having someone check everything. That spreads the team's attention evenly across work that is mostly routine and occasionally isn't. So the exception — the one invoice that needs a person — gets the same fifteen seconds as the forty that didn't.
Where the friction is
Invoices get keyed in by hand from PDFs, one field at a time, because that is how it has always been done. Reconciliation happens once a month, so a problem that started three weeks ago surfaces only when someone sits down to look. Expense claims get chased individually because the policy lives in someone's head, and every claimant learns the rules differently. Reports get assembled by whoever has the least on that week — not the person who understands the numbers best.
Where this usually goes wrong
The failure that costs the most arrives quietly, months in. A vendor changes its invoice format, the exception rate starts creeping, and nobody notices until a reconciliation that used to be clean suddenly isn't. Automation set up once and never revisited degrades like an unread SOP — it just hides the drift better. Someone has to own watching the exception rate, on a schedule, the same way someone owns month end.