This is a really good question, never really pondered it before. Our (U.S.) family had a traditional piper until he died in the 1950s, while relatives and neighbors had traditional fiddlers who dwindled down to a tiny few with few dances to play for, but who did transfer their music to younger proteges during the 1970s and 80s.   What was the difference? In our case, we unfortunately had a few tone-deaf descendants who let the ball drop, whereas the fiddlers had hearing children interested in their musical roots by the 1970s.

At the time the original trad music was being pushed towards oblivion in the 50s, country and bluegrass were showcasing fiddle and banjo in their American formats, while Polish accordions and Irish pipes were odd instruments tied to old ethnic roots which became passe. I know more than one boomer fiddler who came in via bluegrass or 'outlaw country' and migrated to their Irish roots.

As Bill D says, there are now a lot of practitioners out there reviving the pipes (and boxes?), so it's a 'broken' but not lost tradition.   Just some years behind the curve relative to the less broken fiddle story?