The purpose of motorized decks?

I know that armoured is for spearheading assaults through the open, or defending forest. Mech is a lighter armoured deck that can defend towns, and attack more lightly defended open areas. And Airborne can quickly secure land and outflank foes, or spam air/gunships. What is moto good for? Do they try to do fast land grabs, and then try to outflank, are they meant to be a mobile reserve/rapid reaction force, or do they just grab and hold towns?