Abso****inglutely.

Whether you're tripping over an obstacle, your own feet, slipping,etc... stuff happens.

you have a responsibility to not accidentally flag or shoot teammates/innocents during movement or when friendlies cross into your line of fire (hopefully muzzle is down as well)

one way to make that happen is to use the manual safety. with training as people notice it becomes subconscious and doesn't require any conscious thought over time.