Although dedicated loading & unloading bays may useful for loading and unloading, they are also usually only found in warehouses.
Most factories are usually not built with dedicated bays as factories are usually built for production or manufacturing purposes where other specifications may be more important. Such important specifications may be incoming power supply, ventilation, floor trap or water point which are sometimes the basic requirements to carry out manufacturing or production but this would still depend on how your business or company operates.
For warehousing, loading and unloading speed may be crucial due to frequent movement of goods which is why dedicated bays are sometimes a requirement for distributors or logistics companies.
After all, a factory is mainly used for production while a warehouse is mainly for warehousing or logistics purposes.