There's a lot of sheep in Ireland. Outside the cities, they're everywhere you look. I suppose it's got something to do with the climate - you'd need a lot of wool to keep out the winter chill. An Aran sweater I tried one in a shop must have weighed three or four kilos. I really liked it, and it was certainly warm, but I figured there would probably be two days a year where I could wear it in Melbourne.
I'm no expert, but there seems to be more variety of breeds that in Australia, which provides more interest than endless mobs of merinos. They also like posing against all sorts of spectacular scenery, which just adds to their appeal. Irish sheep appear much more relaxed than Australian sheep. Perhaps as there's so much grass everywhere, they never need to worry about where their next meal is coming from.