do_action first default parameter is always blank when not passed

[phylaxis]

I'm having a small issue trying to set up functions in class-plugin-theme-public.php that has a default parameter. I'm not sure if this is a Wordpress issue, a Boilerplate issue, or just me not understanding the do_action method. What happens is I define a function like this:

public function plugin_contact_info( $show_logo=true ) {

    var_dump( $show_logo );

}

Then inside the class-plugin-theme.php's define_public_hooks method I call:

$this->loader->add_action( 'show_plugin_contact_info', $plugin_public, 'plugin_contact_info' );

Finally when I call the do_action like this:

do_action('show_plugin_contact_info');

I would expect a the var_dump to be bool(true), but what I am getting is: string(0) ""

So my question is WHY?

It doesn't seem to be accepting the default as set in my function, or more specifically, the do_action call ALWAYS seems to pass blank as the first parameter if one is not defined in the call. Is this standard for Wordpress? Why would it not pass NULL?