Why can't I use Mouse Wheel Up as Axis mapping?

I want it to return 1 when mouse wheel up, and -1 when mouse wheel down. So I do this in the project setting.


But seems like it doesn’t work. Why is it?

mouse wheel up and down are events, like pressing a button. mouse wheel axis with scale of 1 will do what you want. i use this for camera zoom

because mouse wheel up/down have only one action,unlike keyboard button who has Press and Release 2 action ,so axis mapping can analog the continous event between the Press and Release。but wheel can’t