In Ireland the majority of people over the age of about 40 who drink pints tend to drink Guinness in a pub - apart from Cork where it might be Beamish or Murphy's but as these are all stouts you couldn't tell visually which they were drinking. Lager and Cider are more popular drinks among younger people. Real Ale is generally not widely available in Ireland. and most Irish people I have met who have drunk it abroad tend not to like it much. I disagree but I expect it is an acquired taste as indeed Guinness is.

There is an association in peoples minds between Guinness and Traditional Music, which I think may the effect of subtle and not so subtle marketing by Guinness themselves.

On closing the eyes this has been covered well above. Traditional singers don't tend to think of themselves as entertaining an audience. The concentration is on singing the song well. If the 'audience' enjoy it thats fine, but it really isn't an entertainment thing. The song is more important than the 'performance'.

As for Beards, this has a lot to do with the revival in the 60s when if was a hippie/folkie thing. The likes of the Dubliners would have been very influential in this respect. Three quarters of the original Planxty had beards etc.