The amount of data storage required would be immense and out of the question for many players, a more useful version can be found at EDSM.
You wouldn't need that much data storage.. text compresses quite well.
That said, part of the trading gameplay loop is supposed to be finding lucrative trade-routes. The in-game lore is that systems jealously defend their trading data and prohibit it being advertised outside the system. So it would go against game-lore to include that in the codex.
On the other hand, there's a LOT of general-purpose information which most certainly SHOULD be in the codex which isn't. For example, a full description of all trading commodities, ships, materials, etc including systems likely to sell or trade in them. Basically all the information which could be considered "general knowledge" for members of the Pilots Federation.
Then, of course, the entire "discover your own path" part of the game - the CODEX should contain more and more information as and when you discover it in-game; a sort of personal timeline of notable events.
Unfortunately, as with many systems in Elite Dangerous, FDev did a good job at laying the foundations, but then never proceeded to build on top of them. Perhaps one day..