Biosafety cabinets within a lab are used to work with certain types of bacteria. These cabinets are equipped with a UV light that is used to sterilize the cabinet after it has been used, but many do not use this light as they say it is not effective for sterilization purposes. Why is this the case?

Biosafety cabinets within a lab are used to work with certain types of bacteria. These cabinets are equipped with a UV light that is used to sterilize the cabinet after it has been used, but many do not use this light as they say it is not effective for sterilization purposes. Why is this the case?