Starships: Jump Drives and Complexity
Discovering the scientific principles behind the jump drive, creating the necessary technical base to construct it and getting it to work, hopefully successfully for the crew concerned, is a major achievement for any civilization, if they did it all on their own.
Having passed that threshold, it's not that hard to figure out how to design and build a factor two jump drive, but it seems rather more complex to build one that manages to transition three parsecs in one go. The Vilani never did, or at least, not before the Solomani managed to.
This may indicate a lack of intelligence or imagination on the part of the Vilani, or the complexity of constructing a drive that can jump three parsecs is more than just having a tech level twelve industrial base, but requires a more careful finessing of components than a jump factor two drive, or once you've figured out how to make a factor one drive, which the Vilani intelligence services managed to suppress their colonial minions from progressing beyond, and/or is just that much of the same degree of complexity to successfully manufacture, much as that of a factor three jump drive was from a factor two.
That would mean that jump factor four drives would be even more complex to manufacture and maintain, making most commercial entities shy away from trying to for their commercial shipping, leaving most starships with factor four jump drives in the hands of interstellar navies and rather rich individuals.
That's why a lot of starships, even those built in tech level eleven and above yards, tend to have jump drive factor ones, which are easy to operate and maintain. And that more advanced jump drives tend to be manufactured in high tech tech worlds with specialized factories and experienced engineers.