Kanye has explained before why he chooses not to smile in public in the most typically Kanye way possible.
In 2015, he said:
Back when I was working on Yeezus, I saw this book from the 1800s and it was velvet-covered with brass and everything.
I looked at all these people’s photos, and they look so real and their outfits were incredible and they weren’t smiling.
People, you know the paparazzi, always come up to me, ‘Why you not smiling?’ and I think, not smiling makes me smile. When you see paintings in an old castle, people are not smiling because it just wouldn’t look as cool.
So Kanye doesn’t smile because smiling isn’t cool.