Just like a wood case pencil, the larger graphite core used in a lead holder wears down the same way. It's a tool used by drafters and artists, and you can probably imagine why it is such a useful tool for anyone who uses graphite.
While the Fixpencil version that I have uses 3mm lead, you can find lead holders that use 5+mm lead! That's a thick chunk of graphite! Of course, you can also use different lead grades with these pencils, from the standard HB to other grades on either side. The lead I'm using is 3B, which lays down a thick and dark line with very little pressure. The point wears down very quickly as a result of this, so it's not the best lead for general writing. But, if you're a drafter or artist, you can probably put this lead to much better use. The ability to hold the pencil at a sharp angle and quickly shade in an area is quite a treat. And, you can easily control the amount of lead that protrudes from the end of the pencil. I imagine this comes down entirely to use case and personal preference, but it's something you can only get away with when using the thick lead core that lead holders use.