Frankham: no, it is not just academics who decide what songs should or shouldn't sing. It is the people who sing/play them. I refer you to the current Brass Money set, which does include some tunes "lifted" from a British tradition that does not permit its tunes to be played outside of the traditional event.
Go argue the ethics with Carthy and Kirkpatrick.....but the people inside a tradition can be every bit as "selfish" or "restrictive" as outsiders. Not everyone believes that their music belongs to the wrold - they think it belongs to them.