I've heard several times (citation needed, I know. Anybody?) that processors have gradually been tuned to perform better with machine language that has artifacts from C compilation in it, or something like that. I would love details. (Related: http://www.c2.com/cgi/wiki?CeeAsAnIntermediateLanguage)
Python won't be used as a systems programming language because it's relatively slow compared to most compiled languages (though many parts of its library are compiled C) due to two major strikes against it: It's interpreted (albeit with some bytecode caching), and it doesn't (yet) have a clear way to declare/infer types for optimization, so a lot of cycles get burned double-checking data types. In practice, it's usually fast enough for most purposes -- its design focused on speed of development over than execution, which is a good tradeoff overall, but works against it for systems programming (except prototyping).
Python won't be used as a systems programming language because it's relatively slow compared to most compiled languages (though many parts of its library are compiled C) due to two major strikes against it: It's interpreted (albeit with some bytecode caching), and it doesn't (yet) have a clear way to declare/infer types for optimization, so a lot of cycles get burned double-checking data types. In practice, it's usually fast enough for most purposes -- its design focused on speed of development over than execution, which is a good tradeoff overall, but works against it for systems programming (except prototyping).