In a lot of sessions, people who aren't remotely Irish or Scottish even start SPEAKING in those accents (what is it? an attempt at authenticity?). I think this is unnecessary and try-hard. The accent is usually wrong anyway.In some songs, an accent is necessary (consider "Manura Manya"), but in many, it's not, and downright offensive. How many non-Irish people would know the difference between a Cork and a Wicklow accent? (not I!).
And I firmly believe that when acting, natural voices should be used. The standard of production is usually let down by faking accents badly. So many amateur theatre groups in Australia put on bad American accents when doing musicals, and it's just awful!
Callie