We can't build ships, and they wear out.
There is trade between the "ordinary" citizens of the galaxy, and (say) an "ancient" or "transcended" civilisation that gained access to and mastery of hyperspatial technology a (cosmologically?) long time ago. They value unique items, especially those that they find surprising. Entities with different thought processes to their own are the most capable of evoking surprise, hence the desire to trade. Or so it is hypothesized: they are essentially inscrutable. We only ever interact with avatars, which are uninteresting robots attached to what appear to be tiny ships. They pay for things they like with FTL ships (and any other "magic" you want in your story). They'll build the ship pretty much any way you ask: "value" appears to be a simple function of internal volume. However, a ship is one piece. It's almost indestructible, but if you do manage to break any part of it off, the whole thing and everything inside vanishes without trace (causing a vacuum implosion if it's in an atmosphere at the time. You might draw a parallel with toughened glass turning into small blunt fragments the moment you crack it anywhere. 302
You might also use this as a reason piracy doesn't happen. You simply cannot break into a ship unless you can persuade its occupants to open up. )
It is hypothesized that ships can be made only in hyperspace, that they end up back there when they die, and we don't have the faintest idea how to establish any sort of permanent presence in hyperspace. All attempts to explore the outside environment of a ship while it is in FTL transit have resulted in the disappearance of that ship and its crew. No traces have ever been detected.
It is known that ships wear out. There are known, progressive symptoms of a ship that is no longer in pristine condition. As these symptoms become more apparent, the ship becomes less safe. What happens when it fails is unknown. It is simply lost without trace. The older it gets, the greater the risk of that fate.
The result is that there is never a shortage of old enough ships, and the real question is how much of a desperado you might be. Do you accept a one in a million chance of disappearing without trace to an unknown fate? One in a thousand? One in ten? Ten to one against? 500