There is a proverb...(even elixir turns poisonous when taken in excess) that anything excess than need is poison...For example, Doctor advised to take 2 tablets per day for 10 days and the patient take all the tablets to reduce the 10 days timeline is serious than taking the normal routine of 10 days...Same way, for the lean...we need to consider, the need to fulfill and buffer to a limit will save lot of costs. as example, hotel can stock some perishable goods (like eggs, green vegetables) as minimal stock with buffer and keeping more inventory of them really cost us in everyway...
For example...an Business analysts, available data is inventory where he /she process and add value. Too much of analytics will lead to analytical paralysis...
Too much of demand will increase the costs (not good for public) and too much of supply will reduce the prices & costing to supplier (not good for supplier)...Anything that above / below the need will affect the performance in terms of economic, cost etc.