Why do my service lines get bigger?

[inowhavesolar]

This is a picture of the service lines coming off the transformer and into the meter on my house. Why are the cables from the transformer coupled onto thicker wires? Is this some code requirement that the lines into my house be thicker gauge? Why would that need to be if so? If the thinner wires from the transformer are good, why must these be thicker? It's also thicker wire from meter into main breaker.

 

[B-Mod]

Wires in mast are sized by NEC code. Utilities have their own set of rules and their wires are in free air for cooling of the smaller wires.

 

[MichaelK]

You are not looking at the actual wiring, you are looking at the insulation surrounding the wiring. Might just be wire of a different brand/supplier, or insulation designed for a different exposure rating? Can you actually see gauges printed on the wires?