I look at spearfishing in two ways.
I dive during the day, have fun with my mates, revell in the stalk and hunt, come home with one or two fish, and have a BBQ. This is fine and dandy. Everyone has a great time.
But, I also like to eat a lot of fish, so night diving for me is like a late night trip to the fishmongers. It provides me with a variety of fresh fish in the shortest possible time. It is one of the fundamental reasons why I dive.
Once you get good at it, it can seem like a turkey shoot on some nights. You just have to be selective, take only what you need, then call it a night.