People do care about butter brands. Kerrygold manages to sell at a higher price point than other kinds of butter and make up 50% of the market of branded butter in Germany.

If you go to Lidl they sell Kerrygold for 1.79€ per pack and their own "Golden Kelly" brand for 1,11€. I think Aldi sells a Irish butter brand in that slot, which is a bit less direct about being similar to Kerrygold.

Then there are people who are fine buying non-Irish butter (likely not Grassfed) and people who do want bio-butter.