add_action for wp_head, executing in wp_footer

I wrote a plugin that injects a stylesheet and a couple scripts into wp_head:

function add_support_code() {
	wp_enqueue_style("ramp_css", ".../ramp-styles.css");
	wp_enqueue_script("jquery_ui", ".../jquery-ui.min.js");
	wp_enqueue_script("ramp_js", ".../ramp-scripts.js");
}

add_action('wp_head', 'add_support_code');

I had this break on a specific blog, and I found out it was because I didn’t have wp_footer() in the theme. Adding that fixed things. I looked at my other blogs’ HTML output and the code output also shows up in the footer.

This isn’t really a bug at this point, but I thought I’d learn more about wp_head, wp_footer, and why my add_action would insert this code in the wrong one.