Because every new reporting question gets a new code. Somebody wants spend by branch, so the chart gains a code per branch per category, and two years later there are four hundred accounts nobody can navigate.
Keep the chart small and put analysis in dimensions: cost centre, branch, project, entity. One marketing account with a branch dimension beats three marketing accounts.
Decide dimensions before you post anything. Adding one later means every prior posting lacks it, and you will be reporting on a gap for a year.
Fewer than you think. Dimensions do the work codes used to.
Yes, but prior postings will not carry them.
Usually not — one chart with an entity dimension consolidates automatically.
Half an hour with your own data usually saves reading three of these. The guides will still be here afterwards.