As those worlds cannot afford much in form of roads, they don't have extensive roads (incluiding any form or railroad) networks.
I just take umbrage with this, and it's mostly just the wording.
I pretty much agree with the rest of your post.
But it just makes it sound as if these poor rock farmers just can't make roads (or whatever), and that's just not the case.
For a developing world, there will be as many paths as necessary. If there is an opportunity to be exploited, it will need a road to make that possible. If the opportunity isn't worth building a road to, they won't do it, and the opportunity will lay idle (perhaps as a lightly explored claim or whatever) until it is worth it.
Here's another example.
There is (was) a town in eastern California called Bevridge. Getting there today is difficult and arduous. The trail is very hard, and very badly maintained, and can be difficult to follow. The terrain and climate is terrible. There is no "road". A road was simply not feasible.
But it was a mining town, and the ore was worth digging out.
Instead of a road, they built a gondola system, and used that to efficiently move things up and down the canyon that it sits at the head of.
Today, that system is gone, so it's back to on foot on steep trails in the desert sun, making it most certainly a path less traveled.
There may well be many other mining claims and such out in those mountains that we do not know about simply because the difficulty of extracting those resources makes it impractical to pull them out.
So, a developing world will have as many roads as it needs. Leveraging local resources is always cheaper, but if an opportunity exists that worth pursuing, someone will cut a path there of some kind to exploit it. Just part of the start up cost.