He can't lead people or inspire them, because he can't even lead himself. His goals are promises to others, not to himself. Dragging someone along with him would just be a burden.
He can't navigate; the last time he tried to follow a map he ended up half-dead surrounded by pixie-demons claiming he had stolen their dentures. He doesn't understand money really; except it gets him alcohol. He doesn't see the point in tricking people; if he wants something, there are easier was to acquire it.
He can't shoot things; he is a swordsman after all. He isn't very good at lying, not that he ever really feels the need too. He doesn't invent things because he doesn't really need anything he doesn't have already. He can't tell stories to entertain people, because he doesn't think that made-up tales are entertaining; and he doesn't think anything he's done in the past is all that exciting. He can't fix ships because he's never needed to learn how; someone else has always done it.
He can't cook, at least, not beyond what is needed to survive. It's sustenance that matters, not taste. Though if anyone ever asked, he can make a pretty mean rice-ball.
He can't rule people. He isn't in charge of anyone, and he can't really remember where he's been. Guiding people or saving them isn't really his concern. Stopping wars isn't important as he's usually on his own side; the side that survives.
He can't heal people. He can take care of himself, and that's all he's ever needed to do. He's never had a problem he couldn't fix with a bandage and a little rest, so medicine doesn't concern him.
He can't recite histories or legends because he doesn't know them. He's pretty sure he's never been here before, so he has no knowledge of the terrain. He can read, but he's never been able to sit still for very long without nodding off. And it takes to much energy to quietly torment people and cause trouble.
He's the first mate, because he was the first crewmember. Sometimes he saves the captain, but they all take turns doing that. Sometimes he saves his crewmates, but they really don't need him to. Everyone takes turns at the watch. Everyone can fight.
He's a swordsman; he trains.
He sleeps a lot.
He likes to make sure they don't have too much liquor on board.
And he dries the dishes.
Females apparently have some disorder of faulty genes that makes drying dishes impossible for them.
He can reach the higher shelves to put dishes away, and he doesn't drop them.
So he dries dishes.
No one else ever sticks around after meals; they have other things to do and leave quickly.
He doesn't.
So he dries dishes.
A cook can get the dishes out.
A cook can put food on dishes.
A cook can eat off a dish.
A cook can clean a dish.
A cook can even put the dishes away sometimes.
But a cook can't dry them.
So the swordsman dries dishes.
And occasionally puts them away.
Really, there has to be some other reason to be here, some other reason for the crew to bring him along, because this can't be it.
It can't be because he dries dishes.
He can't really stay focused on reasoning for a long period of time, analyzing anything other than fighting has never really been able to hold his interest. He can't really kill the cook, because the crew would get mad.
So he curses.
And he dries the dishes.
Sometimes he puts them away.