That's just the game and the fact that it's a 1984 single player mindset transplanted wholesale into a semi-sort-of-multiplayer not-quite-an-MMO setting.
Hundreds of thousands of commanders could have scanned those systems and all sold the resulting data to the allegedly galaxy-wide exploration network we're all feeding, but it isn't available for you to buy for the exact same reason that you can't see market prices at the station next door: the universe is unbelievable, has a molecule-deep "economics" simulation, and that's the way it was on the BBC Micro B.