Yes, with thunderstorms and tornadoes, the NWS sends out the polygon warnings for localized areas but these warnings are short lead time warnings and are of short duration. Also, severe thunderstorm/tornado warnings are for weather entities that already exist. Localizing LES warnings, with current forecasting methods and technology, would be difficult as what you said about it not being easy to tell where a band will set up (The entity does not yet exist.). Also, LES bands are fickle as they can hang around for hours and dump snow or they can be in and out in less than an hour as they were this morning. Bands/cells can pop up and dissipate within minutes so it can be like nailing jello to the wall.