It's cultural - centuries of repeated ethnic cleansing meant that only "the portable arts" were possible. In earlier centuries Irish people were good on visual art - come in and have a look at the beautiful early Christian gold work in the National Museum if you're ever in Dublin, for instance. But there wasn't much point learning to make and sell luxury goods like paintings or sculptures or fine jewellery if the patrons were all now impoverished, and the people who'd taken over their land had no appreciation for these arts.

But humans have to make art no matter what, so the artistic urge diverted into stories and music and poetry - well, poetry had always been strong; before the 17th century there were stringent schools teaching apprentice poets with a programme that included lying in the dark memorising a huge canon of poetry all day for many months (must have been terrible for the eyesight) and later learning to compose on horseback. But all that went when the Gaelic lords were disenfranchised and deported to Connacht en masse.