example use case I'd imagine would be something like "I want to send burst emails every 20 minutes from my shared host which doesn't let me run cron jobs. So I'll write a PHP script to send the emails and runmelater to ping the script every 20 minutes"
This was the exact question I had when looking at it (Why do it on your site instead of my own?) Would be great to put this right on the home page in a few bullets.