A more legitimate one would be for videoconferencing -- if you fake yourself in the best possible shape (say, after some weight loss, plus makeup, plus great hair style, plus wardrobe), you can ALWAYS put your best visual foot forward without the hassle/money. So you could be sitting there bloated after eating a bunch of tacos but in a videoconference, look your best.
Similarly, it could be great for film productions: prepare a library of photos in proper makeup/prosthetics, then deepfake the actual footage, allowing the actor to work normally without the time and money spent redoing them every day.
I can't believe you're missing the Snapchat-esque use-case. People are already augmenting their faces, this technology is right up the same alley.
You could transform anyone you're seeing to anyone else. Your colleagues could become the cast of Start Trek. Turn everyone into monsters for the day.
Is it for novelty value or is there a practical reason one would want to deepfake themself?
(Not a criticism, just legitimately curious.)