I'm not an accounting expert by any means but I've been around long enough to see far too many examples of single entry accounting systems that have gone completely off the rails and nobody knows why because meaningful data (i.e. "$M moved from X to Y on date Z by process P") is not captured and difficult or impossible to recreate.

Sure, computers can do basic math and ACID usually works out but that doesn't account for human-level errors. Subtle things like getting an idempotence check wrong can lead to cascading errors that are really hard to see and fix when you just have one view into the numbers.