There is a slight difference. In fallout none of the other towns were accessible to fast travel until you went there on foot first.
I generally use fast travel when I need to resupply or to find a bed to sleep. I see no need to waste time traveling the wilds for ten minutes to an hour before I can level, nor is it much fun to need supplies and wind up fighting off half a dozen things without ammo, potions, or a decent weapon.
I also use fast travel when I have a short time to play and don't want to waste half of it trudging cross country to get to a dungeon or to finish a quest.