Dry hatching is the misleading name given to lower humidity incubation. It does not always mean no water.
The reason humidity matters is because it regulates weight loss in the egg. If the humidity is too low, it loses too much weight, the air cell is massive, and the chick cannot get out. If humidity is too high, there might be fluid in the air cell, which drowns the chick when it pips, or the chick might grow too big and not be able to turn to zip. Candling throughout incubation will give you an idea as to if your humidity needs adjusting.
If you live in a wet climate, then you might indeed not have to add water at all. For me, humidity levels are 24% when left dry, which is considered very low by all standards and causes issues with dehydration of the embryo. I personally have to add enough water surface area to get it to 30 or 35 percent RH. 27% is generally accepted as the bare minimum it's possible to go safely.
Buy a decent hygrometer and then watch the air cells too. Once you are more experienced and know your incubator/climate fairly well you might not need that hygrometer, but for now it's really useful.
