Hello,
phpdocx doesn't use/include StreamedResponse an other similar dependencies for many reasons: the library is compatible with all PHP versions from PHP 5.2.11, many CMS and frameworks don't use it but their own classes/methods to work with streams (WordPress, CodeIgniter...), it's a not needed library as phpdocx generates stream in a generic way that doesn't require using that component, there's a classic package that doesn't use PHP namespaces and other reasons.
Regards.