On Snapchat it’s extremely easy to take a quick photo and send to your friends. Open snap, take photo, edit photo (if you want) and select one or many friends or groups. Doing the same in any other messaging app is slower and more complicated. For me this is the killer feature.
You have to remember the target audience. When they first launched, their app was extremely unintuitive, to the point that it was very regular for someone to show their friends some feature they had just discovered. But that was part of what made it fun: Snap straddles the space between social media and toy in a pretty aggressive way.
And their primary audience of teenagers to young adults eats that up. Hell, it being baffling to "old people" was half the appeal.
I honestly don't care about their UX as no one I know uses it.
It's primary use in my "family life" is as a digital camera toy and for that purpose it's UX must not be that bad because my 8yo daughter is able to find the app, take photos with masks and filter she 'tries on' but not send them to anyone.
FB has almost cloned Snap's features into Messenger and Insta. So, do you think - Snap's UX is still far better?