Actually, for manufacturers, size matters in a big way.
Semiconductor manufacturing is, like with most manufacturing, an imperfect process. In general, for a given die (a die is one "chip" before it's placed in/on any kind of case) and a given manufacturing method there is going to be a manufacturing error rate that is measured in terms of errors per unit area.
These defects can stem from everything from a speck of dust getting into the system, all the way to a gas depositing process making a trace too thin (so the trace, and thus the chip, burns up during use.)
Therefore the bigger the die is the higher the likelihood that any one die will contain one of these manufacturing defects. Since a defect can occur at any point on the wafer, the less of the wafer that can be associated with any particular common point of failure (i.e. the smaller the die,) the more valuable any particular wafer can be and thus increase yield and profit of that product.