When I played RPGs when I was younger (eye of the behgolder 1-2-3) there were standard classes: Mage, Cleric, Warrior, and Thief.A long, long time ago when the World of Warcraft was young, people asked the same question about the Druid class. The Druid could shapeshift into a warrior (bear form), a thief (cat form) or stay in humanoid form and be a healer.
So people asked "What is it's superiority?" since the pure warrior class could still fight better, the thief class had stronger skills and the same went for a pure healer. The Druid could only be 75-80% as good as those pure classes were.
Well it turned out in a tough raid, your tank (warrior) could die, your thief (squishy class) suddenly fall and your healer run out of mana. The druid could step into any of those roles because having 75% is far better than 0%.
In ED, your best medium ship for a role may, for reasons, not be available or not be available in time. And that's why the Corsair exists, it's the Druid class of ED.
If someone had 2 abilities, he had them only at 50%, not 100%.
And yes I didn't play WOW, but when Warcraft1 came out, I was surprised and said - they improved Dune.