Do you have a work e-mail or a work profile attached to your device? Some e-mail accounts enable security on a device that sets what type of unlocking your phone can do, and face unlock is by far the lowest security a phone can have as a printed picture of you can be used by a third party to unlock your device. Check with your IT team to see if such security measures are in place, if so, you may have to choose between having your work stuff on your device, or having face unlock.
