Alan,
It takes precedence because it does. I'm not making this up. Whether or not anyone can find alternate authorities as proof doesn't matter to me. I'm not going to wade through all of the crap sources on the internet that proclaim that -2 squared is -4. They are flatly wrong.
>Ok, I get it now. The unary operator takes precedence over exponentiation because..... you want it to? I tried that philosophy out when I was in school in hopes of perfect scores on everything. Oddly, it didn't work out that way. ;)