We made Done Did because we wanted to celebrate the things our team has accomplished, and we wanted to make it easy for our users to find information about the improvements and bug fixes we've made.
Changelogs are everywhere, but they're inconsistent and sometimes a pain. At best there will be a big file with dates, links to tickets and other great information. At worse there is a commit history. Regardless of where things fall on the spectrum, it's usually not malice. It's just a pain. There are lots of automated tools, but these typically fall short. Writing things up by hand is tedious and error prone.
Teams have it worse, because then multiple people are adding things. Keeping it all straight is hard and someone gets tasked with writing up the Changelog. Worse, few services or products even keep Changelogs that are reviewable or discoverable.
It's important to reflect on your accomplishments and take some time to admire the work you've done. Done Did makes it easy to look over your changes and bask in the glow of your awesomeness. Get invigorated!