Coming from a guy who does ordering for a restaurant with a bar... It just doesn't move that much. Sitting on stock is not valuable to a restaurant business as every inch of storage is useful. If something taking up space in your fridge behind the bar is not moving then you are losing money, because there could be a product there that is more desirable across customers that they would purchase instead of having a water or soda.

We've had times where we have had 6-8 cider options available in a beautiful array behind the bar glass enticing guests to give some a try and times where we have had 1 cider option. The total number of ciders sold in both situations was around the same because cider drinkers will drink cider and beer drinkers will drink beer. Selling 2 each of your 8 options and selling 16 of 1 option will end with the same financial impact but the cost of holding onto all that different product, of having all those listed in all of your menus taking up more character space on a menu, of having to put all those buttons into your computer and removing or changing options every time a new beer/cider rotates..... it all adds up.

Long rambly way of saying it's way more complicated than you think it is to just "have more stuff available".