10 years ago, a person would be insulted for filming a video in portrait instead of landscape. Now, old landscape videos are being cropped and resized to fit in a portrait player.
Insulted? Vines videos were mostly portrait. 2013-2014 were most-likely its hay day. Vines is dead now, but cell phone videos in portrait were posted to Vines a lot.
Now if you mean music videos or cinema, yeah, portrait would be odd.