Why is maximizing surface area and minimizing volume important to cells?
This method maximizes nutrient/material intake while minimizing metabolic demand.
A cell's way of interacting with its environment occurs right at the cell membrane. The more membrane there is (more surface area), the more efficient this interaction becomes. There's more physical room for membrane bound proteins that are needed to intake/expel material.
Larger volume cells have a higher metabolic demand basically because there is more to deal with. If a cell keeps it's volume down but surface area way up (by means of an endoplasmic reticulum or other foldings), it becomes very efficient.