Because this keeps consistency. But you are right that some of the objects change if you change the tileset, like the statue. The thing is that the number of objects a tileset can have is fixed and limited, and until martin-o makes it so that one can make a tileset with as many objects as desired, we thought that making tilesets where some of the "ornamental" objects change would be a good tradeoff. also, it´s true that the objects change, but they´re still of the same kind.