Being a coward is an unhappy fate, even if you know you will never need to face danger. Courage is worth having whether or not you ever use it. On the other hand, the ability to get to Waterloo Station seems to be a useless skill if you're never going to be in London.[note 1] Of course there may be some incidental value in being able to get to Waterloo Station (an eccentric employer whose formative experiences have been around Waterloo Station may require the ability of all her employees) but there could also be similar incidental value in being unable to get to Waterloo Station (maybe an eccentric employer who hates Waterloo Station uses a polygraph to rule out all employees who know how to get there). And it may also be that in gaining the skill of getting to Waterloo Station, one might gain some other useful skill, but that's incidental, too.
Now, maybe, there is some non-instrumental value in being able to get to Waterloo Station. I have a certain pull to say there is. But the following seems clear: there is nothing unfortunate about not being able to get to Waterloo Station, unless you need to get to Waterloo Station or something odd (like an eccentric employer story) is the case.
Are there any virtues that are like being able to get to Waterloo Station, so that it need not be unfortunate that one lacks them? Or is it a mark of a virtue that lacking it is unfortunate, no matter whether one needs to exercise the virtue or not? Let's call any virtues that it is not unfortunate to lack "optional virtues". Thus, virtues can be divided into the optional and non-optional. Plausibly, central general virtues like prudence, courage, patience, generosity and appropriate trust are non-optional. But there may be some optional virtues.
I don't know if there are any optional virtues. Maybe, though, there are some virtues that are tied to particular vocations that it is not unfortunate to lack if you don't have that vocation? I am not sure.
Interestingly, I am inclined to think there are also non-optional skills, skills which it is unfortunate to lack, whether or not you need to exercise them or not. For instance, it is unfortunate to lack interpersonal skills even if you are going to live on a desert island, for then you are lacking something centrally human. (It is, I think, unfortunate to lack legs even if you're going to spend the rest of your life in a coma. That's part of why it's wrong to steal a permanently comatose patients' legs.)
When I started writing this post, I thought that the question of what state is unfortunate to have might neatly delineate between virtues and skills. But I think it doesn't. It may be an orthogonal distinction.