Why is the header not being added when requesting files?

Question

htaccess

There is a sub.example.com subdomain, in its .htaccess folder like this:

<IfModule mod_headers.c>
    Header add Access-Control-Allow-Origin "*"
</IfModule>

When sub.example.com is requested, the Access-Control-Allow-Origin header is added, but when a file is requested, such as sub.example.com/image.jpg , this header is no longer present.

What am I doing wrong? How can I add a title?