Why media formats (like Snapchat Stories and TikTok music videos) become hits?

On September 23rd, Pinterest officially launched a new feature called Story Pins to make it easier for Pinterest creators to “share their talent, passions and creativity”. A day later on September 24th, LinkedIn announced Stories to provide their users “a more human way of sharing”. And with those two releases, an important milestone happened: every single one of the Top 8 most popular social platforms in the US now offer their own version of Stories. That would be YouTube, Facebook, Instagram, Pinterest, LinkedIn, Snapchat, Twitter, and WhatsApp all providing their users a similar vertical media format for telling a narrative using a collection of images, videos, and overlay text optimized for vertical phone orientation.