They have some "real life" historical/conspiratorial significance, and completely unlike a yacht, they're extraordinarily unique in 1879-80. There were airship sightings all over the world (although mostly in the US) starting in 1879, almost 20 years before they would come into common use. In the modern era, they've been lumped into the UFO phenomenon, but there's a real possibility that someone invented one, used it, and then had it hidden (or lost it, or crashed it) and its remains have simply not been found. These sightings formed the basis of Verne's Robur the Conqueror, which is basically an aerial version of 20,000 leagues under the sea, with Robur as Verne's aeronautical Nemo. On that note, if you want to go nautical, why not go for a submersible?
And I think airships are an all-around interesting vehicle (you can even access inland locales) that would make an interesting mobile command center for the Company. After all, it seems apparent that Onieros has a boat - or at least spends a lot of time on one, what with the Ship Radiograms. Why copy? You've got airship plans - might as well use them for something.
All that being said, from an adventuring standpoint, it's generally more interesting if you spend time on transportation that also includes other people. I'd rather run an adventure on a trans-pacific steamer, or the Orient Express, filled with travellers and emigres than on a tiny, lonely yacht.