In the past, products were produced one by one. As the time is changed, people need faster and cheaper products. Manufacturers are able to produce million of parts in a year. But when people need products in less quantity like a thousand, hundreds or even ten in a year? Low volume manufacturing will help.
Source: https://www.teamrapidtooling.com/what-the-future-low-volume-injection-molding-a-570.html