I've checked around 10 sectors where Roguey's map indicated hidden sectors beyond, and only found two. The range of the detector seems very long, the two I found indicated right as I entered the sector even if the actual entry point was at the far side. So unless they can spawn really far away (I checked outside the edge of normal map zoom too) it seems I've gotten a randomly "poor" universe? From reading about people finding good stuff inside the hidden sectors, this makes me a bit miffed if true.
Oh, found this on the confluence pages after making this post:
Spoiler
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There is a maximum amount of possible Remote System Locations. From the this amount of possible location almost half are available to be found, which ones are available for any playthrough is defined randomly.