Snapchat is inherently ephemeral - nothing lasts for more than 24 hours. Compare that to instagram/FB where the feed lives forever. The concept of stories does give people some freedom in sharing things a bit more spontaneous. In addition, they don't have a like button or comments. The only "metric" is people who "viewed" your story. The difference was stark when I first used Snapchat. I believe things have changed now. More people have moved to instagram stories and Snapchat is a lot more "filtered" than it used to be.

IMHO I think they tried to make people share spontaneously instead of a curated feed. Instagram and FB forced a change.