‘Pretty Pointless Traffic Lights?’

This is in a tranquil residential street near us. 

With perhaps one car passing every few minutes and a clear view of the road ahead, one wonders how essential these lights are. 

So often, lights like these cause delay and frustration, especially when they stay stuck on red, and it's obvious that nobody is coming. 
(They are, of course, legally enforceable - see Rule 109 of the Highway Code).

Fortunately, these have very efficient motion sensors mounted on top (extra), which means they change to green as soon as a car or a pedestrian - I've checked - approaches. 

So, no frustrating delays, but I still wonder what the point of them is!