Two important reasons are the public's increasing demand for quality and American architects' growing awareness of copper's unique characteristics. Another factor is the easier installation made possible by new on-site construction methods. And, of course, there's the fact that people like copper roofs because they simply look good. Copper is one of the most thoroughly recycled among what we might call structural metals. Most people don't realize it, but nearly one-half of the copper used in the U.S. today has been used before.
Worldwide numbers are about the same.
One reason for copper's high recyclability is that it's so durable. Unlike other metals, copper corrodes exceedingly slowly in natural environments. That's why those European cathedrals and Japanese temples still have their original roofs. The copper roofs react a bit with the atmosphere during the first few years after installation to produce the familiar gray-green patina, like that on the Statue of Liberty. After the protective patina forms, corrosion drops to little more than a few millionths of an inch per year.