Why do so many people still use redundant HTML tags? The opening and closing body and head tags aren't needed, nether is the closing html tag. It doesn't make that much difference to the page as a whole but it adds another level of indenting to your code and makes it more complicated than it needs to be.
The president of the Federation in Star Trek VI said it best: "Let us redefine progress to mean that just because we can do a thing, it does not necessarily mean we must do that thing." Other than the initial level of indenting, which is basically a non-issue for most people I suspect, there just isn't any reason to omit tags like this. At the same time, they make the markup clearer, and help a reader quickly delinea…
We frequently see things like JavaScript pulled in at the bottom of documents -- the head and body long since stopped having functional impacts, and all they seem to do is make you feel guilty about doing things it seems it's not only pragmatic but perfectly OK to do now.
I guess omitting the outermost HTML tags would disturb me slightly if one wants to keep XML-ish. But then it's always bugged me that XML kind of assumes the "file" has no semantic significance.