Does this include images and such served by Nextcloud?
I mean Nextcloud is PHP-based, so all content is served via PHP, and AFAIK caching is done via the memcache.local provider defined in config.php, APCu at best (php-apcu).
Caching defined in the webserver configs AFAIK should only have an effect when manually/directly accessing files via URL path relative to webroot, so outside of PHP.
Ah okay there is the "Cache-Control" => "public, max-age=15778463",, so this should indeed then have an effect, most likely for button graphics and things like that.
Hmm when you see the Nginx config provided by Nextcloud docs, e.g. jpg and some other file types are explicitly taken out for the regex, but handled in a separate block (which is not required on Lighttpd): https://docs.nextcloud.com/server/stable/admin_manual/installation/nginx.html
Same for the default .htaccess for Apache.
Don’t ask me why it is like this, but I guess there is some reason. But we could ask the devs why it is advised to not set the caching header for png, jpg, bmp etc as well.