I may be on touchy ground here, and I'll ask forgiveness in advance if I step on anyone's toes, but it seems to me that the Irish-American community is far more adept at self-promotion (and I don't mean to attach a negative connotation to that) than Scots-Americans--witness the plethora of faux Irish pubs--and are more likely to extol the virtues of their product than the Scots. Even in the homeland, there is a social phenomenon in which one's own home produce is seen as embarrassingly provincial, and, to be sophisticated, one must embrace product and culture from elsewhere (to my dismay, often from the US--see, I'm susceptible, too). The Irish, it seems to me, are second only to the French in resisting this idea. I often hear Irish drinkers singing the praises of Irish whiskey, whereas the Scots I run into don't feel the need, maybe, and in fact very often don't drink whisky at all. (Likewise, it maddens me to go into a pub with a great selection of real ales and see all the locals drinking Tennent's, or more often and worse, Stella Artois. Not to mention Budweiser...now there's a mystery.)
Maybe some of this has to do with the historical Irish feeling of being oppressed by the English, and the need therefore to assert their identity. You might think the Scots would feel the same way, but their resistance to Union never had the same urgency as the Irish resistance to domination. The Scots were nominal partners, not so much subjugated as the Irish, and indeed the Union of the Crowns was under a nominally Scottish king. Perhaps most telling is the pattern of emigration in the 19th century. Both Irish and Scots went to both the US and Canada, but it seems that more Scots went to Canada, and more Irish went to the US, in accordance with their respective desires to remain in or depart from the empire.
Or so I muse. I'm sure there's someone out there who knows a lot more about this than I do.