Considering how fast and efficient the dockputer is nowadays (mostly) and with all the kamikazes just waiting to pounce, a docking/undocking computer might not be too bad really. Not to mention for landing at high-G planets 
Requires an extra class 1 internal modules weighing a tonne to calculate the reverse algorthm.
The fact that we can do it in 2017 with a crappy $30 computer game is besides the point.
I asked the docking computer and it just said "I'm sorry, Dave, I'm afraid I can't do that."
I would pay real money for an optional Hal's voice.
(or is it HAL's... never mind)
To be honest I think Frontier never liked the idea of automatic moving player vessels in Elite Dangerous and that is why we did not get a auto pilot. The only reason why Elite Dangerous got a docking computer was probably because we had one in the classic Elite back in 1984. Nethertheless Frontier proved their unhappyness with automatic flight in Elite Dangerous by limiting the docking computer start to 7.5 km from starport. In the classic Elite you were able to activate the docking computer maybe 50 km from starport. The dockim music increased in lengh a lot, but the working range dropped near zero. Here you see the classic docking computer working:
https://www.youtube.com/watch?v=L-VJeVPeawk
Same reason the docking computer likes to sit outside the station "waiting in queue" when there isn't a single ship on radar and traffic control cheefully reports "the way ahead is clear" when a Beluga and T-9 are wedged in the slot.