Traffic lights are sort of a 'patch' on them. They usually start off without them, they realise theres flow issues that prevent people coming out of one junctio

Traffic lights are sort of a 'patch' on them. They usually start off without them, they realise theres flow issues that prevent people coming out of one junction, and its going to either be too costly or impractical (space is a massive issue in the uk remember) to switch to something more complex, so lights are used as a permanent stopgap. One example of where this has been an ongoing issue for decades is the Black Cat Roundabout on the A1 (https://en.wikipedia.org/wiki/Black_Cat_Roundabout https://en.wikipedia.org/wiki/Black_Cat_Roundabout). It's gone through numerous changes to improve things, with lights at various points being one of them. Finally now though its being completely redeveloped to a grade-separated junction as traffic has massively outgrown the roundabout.