Bagpipes are not unique to the Gaelic culture. They are found throughout large parts of Europe, the Caucasus, around the Persian Gulf and in Northern Africa, and in Spain.
During the Germanic expansion into Britain after the Romans left, Celtic Britons were often displaced west. Some groups were displaced so far that they fled Britain entirely and moved to NW France (modern Brittany) and northern Spain (mostly Galicia and Asturias). Celtic Brittany managed to stay more or less independent until 1500, which allowed it to keep its own Celtic language and culture. Galicia and Asturias, however, were absorbed into the larger kingdoms of Iberia. This reduced the historic Celtic influence on the culture. However, the Celtic history of those regions was still recognized, and during the Celtic revival of the 1960s and 70s, promoters of Celtic identity took on Pan-Celtic aspects, such as bagpipes, that had not necessarily been part of the culture originally, to attempt to reclaim a wider forgotten heritage.