I would guess that the Garmin devices used in aircraft have the ability to delete waypoints from a flight plan when the pilot is cleared direct to a waypoint closer to the destination. Deleting a Via while driving would be great when the route needs only that change. It would be very easy while driving to go to the Turn List page and delete one via than it is rebuilding the entire route without that point.
If the aircraft versions have a Direct To function, that would essentially be the same and maybe that software could be easily(?) integrated into the drive/walk devices. Having said that, I think I like the Direct To function over the Delete Via idea, but that may cause too many extra lines of code.