Because I think it's a collosal waste of time. The current system map works, it's elegant in it's simplicity & works for any system. in 4,000hrs of play I've never thought to myself 'An orrery map would help here'.We get it, you're not interested in the orrery map. Not sure why you insist others shouldn't be interested either when clearly they appear to be.
FDev clearly have way too much on their hands already without adding stuff like this. I feel the same way about re-colouring the planets. What got pushed back to put that into Q1 2018? Something certainly did.
The game already provides all the information you need to be able to picture how the system looks, and where you are in it imo.