I'm afraid that the answer "Well they are popular in Ireland." Although not a good answer as far as you are concerned is probably the most correct. American and Canadian Folk Song books have a lot of songs that originated in different places on the other side of the Atlantic. Also a lot of them may get printed as Irish because people that don't know much of the history of the song associate them with Ireland, its a marketing game. I like to sing songs from all over the Britsh Isles but generally say that I sing songs from England and Scotland because otherwise people assume I sing a lot of Irish or "CeEtic" music which doesn't really do justice to the fact that I sing what I like wherever it comes from.