When you begin to teach other languages from English, how will you deal with lexical stress that is unmarked in writing? Will you underline, bold, add accent to the stressed vowels? The stress placement is very important in many languages, e.g. in Slavic languages, and there are quite a number of minimal pairs (pairs of words) that are distinguished solely by the position of stress.
Of the current languages that are taught, German has lexical stress, but nothing is done to show it.