Simple... a lot of Irish music is fast, exciting and loud, and appeals (for listening especially) to folks who are not necessarily aware of its history. It also features 'tunes' to dance and clap to more often.

At the Smithsonian Folk Festival in Washington, D.C. for a number of years after highlighting Ireland and Lousiana, they tried each year to plan themes which would justify having either Irish or Cajun music... sometimes both! They would take food, workers, crafts, ...whatever... and sneak some degree of Cajun or Irish into it because it always drew crowds of folks who liked to dance and clap along.

*I* happen to like English & Scottish traditional music better, but it takes more ... ummm... 'awareness' to get the words and significance. I am lucky to live in a area where we DO have a decent selection of all sorts... but even here, Irish pubs get the big crowds.