Note that this is not a question about how to change / edit a CPT’s description. It’s more about “why the heck is it provided?” because I haven’t found anywhere either in the Admin back-end or the front end, where this description is actually shown.
What am I missing?
There’s not really a good usage of the description in WP. However, if you wish to extend the WordPress functionality and use the description in your theme or plugins, it’s available to you with the following:
global $wp_post_types; $post_type = 'my_cpt'; $description = $wp_post_types[$post_type]->description;