Anglo concertinas (originally "Anglo-German") took the German fingering system and applied the higher-quality construction methods of English concertinas, and these were more expensive. Most working class people played cheap German concertinas. German concertinas were cheaply made and whilst not exactly disposable had a relatively short life even on land and would simply be replaced when they could no longer be repaired.

I wouldn't call either melodeon or concertina 'fragile' although like any instrument they need to be treated with consideration. Most instruments would be susceptible to damp, and the main risk to free reed instruments at sea would be corrosion from the salt air, but this would not affect brass-reeded instruments.

I wonder how the melodeon and concertina came to be taken up by the Inuit if not from sailors?