For US government travel if you look at the State Department web page it mentions that the perdiem rates are set as such to 'substantially' cover the cost of lodging and meals. Maybe your employer had a similar policy. When I used to travel on full per diem it was only very rarely that I would ever exceed the State Department rates, but often times I would meet the lodging rate because certain hotels in some countries always seemed to set their rates exactly at the maximum allowed US per diem rate.