The flange is the circle where are put the spoke heads.
Rule number 2 : flange diameter impacts the solidity of the wheel :
Bigger is the flange, shorter will be the spokes, the stronger they will be.

This picture shows to 2 generations of Shimano Rear Hubs.
Left Hub (the smallest) is perfect for a 26 inches wheel, but the second will be used to build stronger and bigger wheels.

Now, hub makers are making hubs that are lighter and smaller.
Modern Axles are often made of aluminium, but steel axles remains the stronger and longer lasting choice.

Hand build La Fourmi Wheels uses Hubs with larger flanges and steel axles for the strongest wheels.