There are market studies that show vertical video is more effective in mobile advertising because 1.) attention spans are shorter than ever, and 2.) 99.99% of people are holding their phone vertical all the time.

I think you’re looking st it from the perspective of a videographer, not a consumer.

Consumers aren’t going to rotate their phones to watch ads. You can’t rotate an Instagram post. This is the new media landscape, this is how things work now. There will always be a place for widescreen but right now vertical is uncharted territory that’s starting to be explored.

Source: just wrote a paper on it for a media research methods class I’m in.