Disclaimer: I’m neither a WordPress guru nor a PHP expert. This is what it is, a dirtly little hack, otherwise I’d have called it an “enhancement” 
Now onto the main things.
Aim: You would have used wp_list_pages (or plugins like dd-list-subpages, that use it) to display a list of your pages/subpages on a particular page. e.g., I use it on my “Projects” pages hierarchy to list all the relevant projects under a particular heading. Now, the thing is that wp_list_pages gives you a lot of options to display things like dates, page title, page link, etc, but that’s not enough. I need to provide a small description for each page as well, to put things into perspective. Obviously, I don’t expect the visitors to go inside each link to see what it holds in store for them.