What makes Martial Arts useful is that they are prepackaged combat styles which require little to no thought for players and STs to invest in.
Instead of having to buy a cloud of Charms from three to five different abilities, you invest in a single Charm tree with a predefined path that, when complete, gives you a total combat style. Or that’s the idea. Lots of Martial Arts Charms did not, in fact, fit this ideal because those sucked and missed the point.
Martial Arts was supposed to be worse compared to straight ability because it could do all sorts of things the other abilities did but worse. You got second rate dodge and parry and soak and attack Charms, because if you wanted first rate Charms you invested in Melee and Dodge and Resistance.
And the fact that the trees were self-contained was a benefit, because it reduced the player’s need to think too hard about what they were picking up next. You got, what, one to three choices in a style at any one time and those rapidly closed off. So a character who invested twelve Charms into a single Martial Art should have a complete combat suite they can fall back on without having to pore over dozens of Melee and Brawl and Archery and Thrown and Dodge and Resistance and Integrity Charms.
And for STs they are a blessing, because it means you can say “Snake Stylist” or “Fire Dragon” and you were done designing an opponent. Thus, because each martial art had its own theme and method of fighting, you could build “Generic Dragonblooded Monk” and drop one of five styles on him and suddenly you had five unique opponents at your fingertips for one fifth the work. And multiple that by an order of magnitude if you allowed the “Monk” to have heretical styles or Terrestrial Styles.