FCs do have the ability to buy a workshop for building airships if their FC has a home, just as happened in the case of that NPC. Many FCs even build airship parts to sell to other FCs for use in their own workshops.

I think what you're really questioning is the function of airships. Airships as actual mounts are problematic from a technical standpoint, which is why we have them for automated exploration instead of player character transportation.