The writing on the back says it's to commemorate the coronation of HM Elizabeth II, so it's over 70 years old. It's in quite good condition, given its age and the fact it's covered in moss. It's in better shape than I am, anyway.
Maybe people don't sit on it because of that missing vertical in the backrest.
Alternatively, the may prefer the cute, roofed, wooden bus shelter four metres away from it.