I have tried to use the unlocked mode but I can't seem to even get used to it. Constantly moving the screen, to me, is frustrating and tedious. When I try to land skillshots in unlocked mode, I will usually move the camera to my enemy, however, the screen is not big enough to let me see myself, so if anyone comes to gank from behind, I won't even notice it and will have a hard time to react quick enough before I die. The vision problem for the purple team is even prominent for champions that heavily rely on skill shots like Lux, it's harder to aim as you are not able to see the enemy champion easily.
People have been suggesting 90 degree turns to the map but I feel that I would be most comfortable with a 180 degree turn so that it would be exactly like the blue team. The only thing different would be the river and the dragon and baron positions.
Maybe Riot does not want to change the purple team because it is going to be harder to explain where some objectives are as they will differ with the blue team which might occur even if a 90 degree turn or 180 degree turn would be implemented.
All this is just my point of view and speculation so I may not be accurate and this might differ from your user experience and perspective and in that case, I would gladly hear about them.