By making a mold, we can produce the same shape exactly and in large quantities.
Actually, it is expensive to make the mold, but if you have a prospect of selling the product, you can lower the unit price of it. You may consider making it depending on what to sell.
How accurately can a mold be created? For a high precision mold, it can be as precise as the one with an error of about 10 micrometers.
Speaking of 10 microns, how do we compare it with our daily life objects? The thickness of the hair is about 100 micrometers and the diameter of the particles such as flour and starch is about 50 micrometers. You can see how a mold can be really precise.
On the other hand, in order to accomplish such degree of accuracy, the material of the product must be carefully chosen.
For example, metals tend to be slightly expanded when removed from a mold, but plastics tend to be shrunk when cooled down.
Also, when fabricating it in large quantities, you have to take the wear of the mold into account. You may have to use a hard material to make the mold, or you would polish the mold to maintain shape.