Yes, as Jason says, the huts (with exception of the Great Walks) cannot be pre-booked, so you risk turning up to a full hut and no where to sleep. And sometimes due to track conditions, swollen rivers etc...you don't make your anticipated hut. A pad and bivy or tarp would be a minimum that I would carry.
"Any must check out hikes that have zero huts?"
Depends on what level of hiking you plan on doing. But the most popular tracks all have huts on them (that might be one of the reasons they are so popular). We actually go out of our way to avoid huts, so it's a personal style thing.