I can only echo what many have said already. Because the orbit lines are rendered so flawlessly (unlike HUD elements, which bounce around a bit) and because they are masked behind the cockpit ironwork, to me they always served to underscore the artificiality of the rendered world outside the spacecraft. As soon as the option to remove them became available that's what I did, at which point the galaxy became less like a planetarium and more like a series of actual star systems.
At first I missed the proximity warning circles, and the rather satisfying burst of lines when an exploratory honk revealed an unusual number of new planets, but it didn't take me long to adapt. I've recently returned from a week's exploration and didn't crash into any stars while scooping; after a while you learn to interpret the rate of change of both the fuel flow and heat, and in conjunction with a visual on the star's corona it's almost as good as the range circle.
The lack of orbit lines when approaching stations can be mitigated by flying a slightly wider approach and looking for the parallax between the station and whatever it's orbiting. After a while that too becomes second nature. I did the Mobius Rares Race this way and although at the time it felt as though turning the lines on might have helped, I'm not convinced it made that much of a difference in the end.
I'll add a virtual +1 to the request for a bindable toggle, although it's fairly minor in the grand scheme of things. As I've said elsewhere it would also be nice if the system could be configured to temporarily illuminate the lines for a couple of seconds after a successful discovery honk, just to give a quick eyeball overview of the new system, but I appreciate that's possibly one option too many. KISS and all that.
I'm just eternally grateful that the option to turn them off eventually materialised. For a long time the answer to "can't they be toggled?" was a resounding "no, and never" but thankfully someone saw the light. I would still have played the game with them on, but it wouldn't have looked nearly as convincing to my eyes.