Why doesn't the large hydraulic shovel have a blade while the small one does?
The main job of a mini shovel is to dig and lay water or gas pipes and plant trees at parks and side roads. Once you dig the ground in parks and side roads, you have to fill in the holes later. However, even the smallest bulldozer such as Komatsu's D20A is often too big to get through parks and small roads. This is why a mini shovel comes with a blade. With a blade, it can fill in the holes it digs.
As for Komatsu, PC-MR and PC-UU series come with a blade, while the large hydraulic shovels such as PC400 and PC600 do not. The large ones' job is to dig the ground at big construction sites or dig a big mountain and load up a dump truck. Since the job does not require filling in the holes, a blade is not necessary. Mini shovels and large hydraulic shovels serve different purposes at different places.