kagrenacs:

I like to think the detect life spell is often used by healers to see how fast a person is fading or if there’s any life still left in them. If a person is healthy their glow is intense, if they’re hanging on by a thread the glow is dim.

It’s also used for checking areas where a large mass of people died in order to see if anyone’s unconscious but still alive, or areas that aren’t easily accessible/dangerous so nobody else has to die.