Without getting too much into it, the Catalan are an ethnic group in northern Spain -- some support Catalan independence from Spain and there is a distinct identity different from that of the Spanish. It's not unlike the Quebeçois versus the Canadians.
They have a different language and would consider a sign by Apple in Spanish to be insulting. Apple has long had signs in its Barcelona stores in Catalan.
Yep. The same is true for South Tirol in Italy having German and Italian signs everywhere, Elsass/Lothringia in France (German/French), many areas in Switzerland having 4 national languages (German, French, Italian, Romanic), a region in southeast Germany (German/Sorbic), a region in northern Germany (Swedish/German), Belium (Dutch/French), and that is just the different signs in the not-national language I've seen in Europe. It is all about preserving the own herritage and culture. Humans need their history and culture. Without knowing the own, how would you be able to understand the others?