What is a .dead file for?

When I uninstall some apps, they leave behind their install directory along with .dead file. It seems like it's specific to Electron/Squirrel applications. Slack is a prime example.

What's the point of this file? What purpose does it serve? Shouldn't an application remove itself entirely when uninstalled aside from user data?

.dead file seems to be created when you uninstall a squirrel app: https://github.com/Squirrel/Squirrel.Windows/issues/943#issuecomment-338869343

Update 26-06-2020. Moved from my comment to the answer, as requested. The purpose of the file as described in the link above:

Squirrel is adding the file to indicate the app is uninstalled, but it couldn't delete the directory. The FullUninstall method will not work on a folder with .dead file and the clean algorithm (that runs on pc startup) will skip these folders. From the code: "NB: If we cannot clean up a directory, we need to make sure that anyone finding it later won't attempt to run Squirrel events on it. We'll mark it with a .dead file"