D&D 5e has a few spells that duplicate some effects of experienced player characters. Here are a few examples–Aid, Cure Wounds, Mass Heal, Bless. One way to think of them is this: these are the “missing” spells from players’ spellbooks that will often be used by NPCs because they’re so iconic but not as good on the table-top for either side.
So when we discuss why it’s appealing in an NPC context, bear in mind what might be the NPC character’s purpose. In most instance with Aid and Mass Heal as well as Divine Favor or Sacred Flame (characters most likely seek out these options after other resources have been depleted), I would suspect it to be about gaining/increasing influence over an enemy or ally, preventing/removing negative conditions that might impact the players’ ability to be effective, or incapacitating someone. It’s also possible it could be about infliciting positive conditions on the NPCs’ allies–like Mass Healing Word for example.