A.) It's an 'OHSHIT I NEED TO HEAL RIGHT NAO' that doesn't take a year and a half to come off CD (Benediction) - I've used this plenty of times to Bene one tank on the brink, then Tetra the other thats about to be on the brink when shit is hitting the fan and any delay to cast a cure WILL result in their death in between. Just boom, boom. Crisis (mostly) averted.

B.) "I need to heal this person but I can't stop moving (like T9's rotating, unpausing Heavensfall explosions) or we're both dead".

C.) "Oh shi- all this healing made me out of MP! And the tank is about to die! Tetra dis!" (no mp req)

It's not as potent as cure II, but it's better than death in the middle of casting and it's better than not being able to bene an emergency again, for a looooooong duration. Alexander floor 4 is prime usage for me, for them both skills - for namely A and C.