From the pictures, it looks like all it is doing is dragging material down the road. This adds a big load and requires a lot of tractor to pull it along. Note in the picture taken from behind, that it is not leaving a good smooth top layer for a good road surface.
For road maintenance, you need to be able to angle the cutting edge to get under the high spots (bumps) and at least to the bottom of the low spots (holes). Similar to a road grader. If the blade is square to the road way, then it is difficult to do anything with the surface other than cut off some bumps, and let it drop into the holes. The road material has to be worked up and spread out and then packed down.
A rear blade that will angle and which has the trailing wheels such as this rig would be close to a grader. These straight blades are good for having a lot of tractor time, because the roadway will need to be re-repaired often.