I use braid all the time without as well, but I will add a leader if I think it will make a difference, or I don't want all that strength from braid, but want all the other characteristics, like no stretch, limp line. One example would be for fishing jigs in trees. Adding a leader, say 10# fluoro to 50# braid, for fishing jigs in lay downs makes sense. If I get hung up, I can break off without too much commotion. The bonus is being able to feel the connection knot when your line is draped over a branch. If I know I have a 4' leader, when I feel the knot, I about when the jig will hit the branch and I can use more finesse to get it through.