Why doesn't a small bulldozer have a ripper?
It is true that while most of the large bulldozers have rippers, the small ones don't come with them. The larger bulldozers are usually used at gold and diamond mines or at a gravel quarry where the ripper becomes really handy when they need to break big chuncks of rocks. On the other hand, most of the smaller bulldozers are used to level the ground at road construction sites. At those sites, there is no need to break big rocks, and therefore they are not required to have a ripper.
This does not mean that small bulldozers can not have a ripper. There are ocasions when a ripper is attached to a small bulldozer so that it can soften soil that is too hard for a blade to shave. It is just like plowing with a hoe at a field.
Bulldozer [THE GREAT PICTURE BOOK OF CONSTRUCTION EQUIPMENT]