Because there can be many, but has many disadvantages, for example, there is a niche in the work piece. Low mechanical properties and molding that is used with a short lifetime, thus causing a very high production costs.
Because they can be mass produced But there are several disadvantages, such as cavitation process. Mechanical properties and low mold used last for shorter and thus the production cost is very high.
Because it can produce many, but there are many cons such as sinus in the workpiece. Mechanical properties and low die used short lifetime and caused the production cost very high.