Entertainment (memes). Trying out a new hairstyle matching your face.

The hairstyle thing sounds like a killer feature, but I think that it would be relatively quickly overtaken by whoever makes it easier to create 3d models of yourself at metahuman-like level.

Putting yourself or a friend in a movie scene, for example.

Lol, literally what I use it for half the time for meme reasons.

Digital marketing agencies can make website team pages look much more professional without having to go to the expense of a photo shoot

Perhaps this is a bit cheeky, but I think it'd be pretty hilarious if a company, intentionally or otherwise, used this to generate a bunch of uniform headshots that made all of the employees at a company look like they're in way better shape than they actually are.

So the model and photographer lose their job but the company bottom line is unchanged.

I use Roop (which this is a successor of) to make stablediffusion pictures of myself (e.g. for my slack avatar).

Amusement. Putting your mates in a film scene. Making silly memes. Etc.

Not everything needs a “serious” usecase.

It does where the negative use cases are very harmful. I can think of many fun projects I could pursue in my chemistry lab if only the precursors and equipment for mass producing nerve agents and high explosives were not tightly regulated.