Why do elevators show current floor number only on ground floor?

Now, this may well be something I most commonly notice because I use old elevators (from the last couple of 15 years), this caught my eye: current floor indicator is only on ground level. Though the elevator does contain a display with the number of the current floor passing by (which is automatically updated), all other floors (both above and below the ground level) only have direction indicators. So, if you are at the 11th floor and you want to go down with the elevator being at the ground level, pressing the button will only notify you that the lift is going up; you will not know from which floor it has started.

I understand that this might be a cost-cutting issue but all the elevators I have used, no matter if they are at a small or a large building, newer or older, hotel or public service have the exact same setup. There is a minority that do contain what I am asking but as far as I am concerned, this is the default where I live.

As the elevator is moving away of the ground floor and both the ground level and the elevator itself contain LED indicators with the current floor number, we can safely assume that there should be wiring that goes across the elevator shaft (either to send or to get the information of the current floor number, depending on where this "circuit" is installed). And as all floors have LED displays, just not configured to show floor numbers, I cannot get why they don't plug them in to show them. Where is the cost-cutting in that?

Note: Of course, I know that we can find hundreds of examples with lifts that do show numbers at all floors, but I can find a causality in all the cases I have seen, so might there be a smarter explanation than just the "we didn't want to spend more money" excuse?