Completely impractical if the danger is hidden until you get there. Children and animals dashing across the road. wheel smashing potholes full of water that the council can't afford to fix because they spent the budget on speed cameras sleeping policemen and totally unnecessary traffic lights. Old truck brake drums dropped from pedestrian bridges by bored teenagers.
The list of 'stuff that you can hit that wasn't there last time you looked' is endless.
Maintaining idealised safe distances is an idea only people who don't really do much driving believe in.