When I worked for Uncle Sam, Government workers re not permitted to fly business class except for travel that exceeds 14 hours. So they are not filling the business class cabins.
There is no incentive for UA to make additional saver award space available so long as DL and AA offer even worse options. Most first world mileage programs Eg BA, LH are no better. AS is probably the outlier but isn’t strong enough to steal UA international customers esp after gutting the popular VX flights.