On a digital console, you've generally got layers. That is, there aren't enough actual faders to control all the channels, so you have to switch between layers for 16 faders to control 32 channels. When switching layers, you need the faders to revert to the positions that represent the settings on the selected layer. Similarly, on some consoles (e.g. Soundcraft Si Expression), a master fader might perform multiple functions. On that console, there's a fader that controls the mono out on the main layer, but it becomes the aux send master when an aux send is selected. In addition to all that, you can have functions like having one channel on faders to all the aux sends (rather than all the channels into one aux send). Even further, the channel faders can be converted into a giant graphic eq (which, in the case of the Si Expression, requires two layers to cover all the frequencies). None of these functions would be practical without motorized faders.
