Why S&OP often disappoints in practice
The method itself is sound. What undermines it is usually the machinery around the meeting.
Packs are assembled by hand. Analysts spend days pulling figures from several systems into slides, and by the time the meeting happens the numbers are already out of date.
People debate the numbers, not the decisions. When demand, supply and finance each bring their own version, the time goes on reconciling them instead of on choosing between options.
Gaps between plans stay hidden. A mismatch between the sales plan and the budget, or between demand and capacity, is easy to miss in a static file.
Decisions evaporate. Without owners and deadlines recorded somewhere visible, actions from one cycle are forgotten by the next.
Nobody can see what changed. If plans are overwritten each month, it is hard to learn from how the forecast moved or who adjusted it.
