...is because they haven't visited any of the more exotic systems. I only today managed to build myself Warp Reactor Sigma. That means - as well as just the systems represented by yellow stars - I can now warp to red systems too. These are more likely to contain more rare and exotic resources and wildlife. And that's just the first tier; folks keeping an eye on the upgrade system may have worked out there are three levels to any upgrade: sigma (level 1), tau (2), and theta (3+). Pertaining to star systems accessible with upgraded warp drives, this means that there are still two tiers of rarity I've yet to discover - green systems and blue systems. Considering my very first planet in a red system was sprawling with gold, and traders were offering stuff I'd never heard of, I'd guess the bulk of players have yet to come across much beyond red systems. The good news is, I already have a tau blueprint.