A lot of setups route audio through the TV so if you turn it off you turn off music / podcasts which a lot of people use to sleep. (including the author, as noted in the article)

Most televisions do not continue playing audio when they are turned off.

From the project page:

"That second paragraph hints at why this is important, despite the app’s simplicity."

and the second paragraph on the simulated display:

"Use this app when you want to listen to a podcast or music without seeing artwork or a screensaver."

facepalm I read that paragraph, but my brain skipped that sentence for some reason. Thanks for clarifying

tvOS allows you to play audio in the background - Blank allows you to blank the TV while still having the background audio playing from the speakers.

That’s the joke :)