It's the same for most cities and even towns, I'd imagine, eg. Sheffield (baffling one-way system to visitors), Birmingham (one way streets, central road by New Street actually leads to an underground car park if you're not a bus), Coventry (roads that go nowhere in the city centre, bus lanes that appear and then disappear after only a few hundred metres, cut across roundabouts etc). Try Redditch with its unnavigable ring road system - how do you actually get to the Vue cinema in the central shopping centre, even with a GPS??? Even towns with a grid layout (eg. Leamington) have no right or left turns across the grid so you have to follow a certain route around the town.

I think it's just symptomatic of hundreds of years of town growth.

Probably because its been "designed" over a couple thousand years and they don't have cars for the majority of that.

I doubt many donkey and cart owners encountered the no right turn onto Piccadilly! All of the things I mentioned are very much 20th century additions.