Maybe one reason why people don't treat tests as code is that in "Refactoring" by Martin Fowler he wrote:
"A difference between test code and production code is that it is okay to copy and edit test code" (#)
Jim Weirich agrees that there is a slight difference:
In tests, when faced with duplication vs. readability, I tend to favor readability in my tests a little bit more than I do in my production code.
Ben expressed a sentiment that tests are potentially more important than code, since nothing tests the tests, but Uncle Bob disagreed, saying that the code tests the tests. He did agree, though, that given tests you can build the code to make them pass, but not the other way around.