I think a non-pedalling throttle-only mode would be useful, even with a low speed limit e.g. 5 mph.
Today for example, the road was closed to cars due to a lake in the road, it was about 200m long and 30 cm deep. Cars were turning around but of course I am higher up so gave it a go.
Water came up to the bottom of my hub motor, submerged my motor controller and pretty much level with my bottom bracket (hopefully all well sealed!).
I was able to get through okay, bike was fine (so far), but my feet were soaked because I had to pedal! On the downstroke the water submerged my feet. If I didn't have to pedal my feet wouldn't have got wet. I blame the EU for my wet feet.
Also on ice, snow, it would be useful to feed in a small amount of power, and concentrate on staying upright rather than pedalling.
Both of these are low speed applications, and a thottle up to 5 mph would be ideal.