Basically the people in our college who spent most of their time smoking weed/gaming/partying instead of studying, who got mediocre grades and didn't really learn anything, and who subsequently discovered (due to those decisions) that they're mostly unhirable after graduation, ended up going overseas to teach ESL. It was such a common occurrence that it became a running derogatory joke on campus to describe an underachiever.
Companies and institutions out there need to figure out a way to screen applicants harder and more effectively.