>>4014189People have all sorts of theories about how this is a primate style expression or that it conveys anything, but the reality is that it is much simpler than that.
Men who make this face are men who are uncomfortable with the way that they look, more specifically their smiles. In photos they will be hesitant to smile because they fear that the resulting photo won't make them look good so instead they make a "wacky" face. This means that they can still project the same emotion as a smile (being happy/excited) but without the risk of looking bad that a regular smile would provide. It all boils down to a fragile self image.
This is the same reason that women make duckfaces in photos, they too are uncomfortable with the way their face looks.
This same base emotional fear is the reason why Will Farrel starts singing gibberish partway through his performance here (starts around 2:50):
https://www.youtube.com/watch?v=OlLzAWUY6Xoas he is afraid to genuinely sing due to a dislike of his singing voice and a fragile self image (extremely common in comedians). This is also why you will sometimes see footage of people playing videogames (in a stream or a video review) where they will begin to lose or take a lot of damage they will start "goofing around" instead of actually playing.
tl;dr people make the soyboy face because they don't like the way their normal smile looks.
