This is an old question ported over, but a good one. One of the things that is unique about ESPlanner's Monte Carlo function is that it is showing probabilities (upside and downside) on the household discretionary spending (living standard) not merely on the pool of retirement assets. The conventional Monte Carlo analysis is programs says, in ordinary terms, "you have this or that percentage chance of running out of saved retirement assets."

But if said "retirement assets" contribute to a very small source of one's living standard, this may have very little impact on the annual living standard (Social Security, a pension, and a annuity, for example, may comprise the bulk of one's living standard). Or it could make up a very big difference in other cases. So without seeing the impact on annual living standard, you simply haven't learned very much that is interesting from the Monte Carlo analysis.