First, using it for the content type makes no sense either, because you have to assume it is text/html to parse it, and if it says anything else, what the hell is THAT supposed to mean?
As for the character set, that would mean you first have to guess the character set used, parse the file, find out the real character set (assuming you guessed right the first time and could parse it), and then re-parse if you got it wrong. This is not a behaviour you should be relying on.