Just beyond the wall is the park where the children play. Parents have a perfect place to sit. The only problem is they’ll have no space for their legs or maybe some difficulty in getting a good view.
Maybe the seat was specially designed for people who wish to examine the surface of the wall instead of for those who actually wish to enjoy a wonderful view.
With so many cycles in this picture, it seems that people have used the bench for parking bicycles instead of a place to sit.