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 delineate between two important sections of the document. Therefore, since they provide at least a very small positive benefit, it is perfectly reasonable, IMHO, to include them.