Header and footers are imported as separate segments and it seems that they are placed at the beginning of the file.
There could be situations where the headers and footers are made up of automated references like for example, chapter name or page number or file name. These would be replaced by tags in the editor, and might not even been displayed at all if the segment does not contain any translatable text. The is true with table of contents or other Word fields. But they are generated based on content from the file itself so no translation is needed.