Universal Acceptance of Copper
In the 1930s and later, there was a tendency throughout the country to use aluminum or galvanized steel wiring, which would later cause problems when it aged and became brittle, and then would arc or spark and have the potential to cause fires. Many areas of the country still have homes with aluminum wiring in them, although it is prohibited by code from use in new construction or retrofit applications. Solid copper wire is not prohibited by code and is excellent for any electrical application.
Copper wiring stretches much better than the aluminum or galvanized wire. This makes installation easier. Further, the structure and framing of a home can experience slight variations over time as wood expands and contracts and as the house "settles." These shifts can be imperceptible, but it is still best for wiring to have some "give." Copper's flexibility means that it will not break down from repeated use and cause shortages within the wall or within electrical outlets.
Lesser Oxidization Issues
Copper wire is also much more resistant to surface oxidization that is a problem with aluminum electrical wiring, and as a result, copper wiring will not have oxidization issues like aluminum or other types of wiring over time.
Ease of Installation
Most people who are handy or who have experience in the electrical field can safely and easily install copper wiring, whereas other types of wiring may be difficult to install or they may have problems working with the non-copper wiring.
Copper will not break if it is overloaded. This means a copper wiring system can safely withstand an overloading situation, making it safer for use in residential applications.