its because they are so scared stiff of solicitors I'm afraid. There was a little triangular traffic island coming up to a roundabout in Donny nudged about a foot one way ... at what cost? I suppose they had to move it to adhere strictly to the regulations when another part of the junction was changed but in reality it was just a waste of money. I remember seeing some stupid bike lanes drawn on a plan for an office park, the sort of cycle paths that go onto a pavement with a give way sign when it comes back onto the carriageway .... I pointed out (as a cyclist) that no-one in their right minds would use it .... as indeed they wont ..... and the traffic consultants knew that as well, but it's just part of the game of not getting sued if someone falls off.
New junctions seem to attract forests of traffic lights now ..... how much does it cost to erect one pole with traffic lights on it???? there are always 3 or four duplicates ... (£40K ?) ..... only there because if they weren't, the council would be sued - contrast that with French traffic lights, where instead of having a duplicate set on t'other side of a junction just so the first car driver can see it, they put a mini red, amber, green set halfway down the pole so he can. That would save the cost of a new pole, connection, big set of lights and the foundations etc. but no one at a local authority would ever have the drive to try to campaign to change the regs.
A related subject shows how little British citizens are trusted by our authorities compared with drivers from some other happier nations ...
Americans can always turn right at a set of lights even against a red, if it's safe ..... how often are we frustrated by not being able to turn left at junction despite there being no possibility of a crash?
French lights are turned off and left flashing amber all night after a certain hour when the roads are quiet - they leave it up to the driver to make his own decision and credit him with a bit of common sense .....
By way of contrast the authorities in Blighty don't even trust us to vote sensibly in a referendum