I admit I don't get it
And I'm pretty sure it's not me. I'm as 'digital native' as they come, despite approaching 40. I'm a user not an IT-bod.
Snapchat doesn't doesn't appear to have utility. It simply doesn't do much. It's very ephemeral nature is it's greatest downfall. It's speed reduces the quality of communication. It's utterly empty and bereft of any kind of meaning.
I have teens who use it. And they're sending a near constant stream of pictures. Each takes no more than 10 or 15 seconds to compose, snap, edit and send. Which means it's taken virtually no thought. When each message it received, it stays only for 10 seconds. Imagine looking for meaning in something new in ten seconds?! It has no meaning.
It's almost telepresence. But that's all. "I am here and friends with you". That's basically it.
If you composed a message or an image with meaning, you'd surely want it to stay around? If you received something of interest or with value, you'd want to keep it. At least for more than 10 seconds.
As for the parent's stuff - we didn't want the kids to have it, but dad allowed it. "It's fine," they said "it tells you if someone takes a screenshot". Bit late by then, isn't it? We have since dealt with a 14 yo sexting and a stream of illegal bullying messages disappearing, leaving no evidence to have it dealt with. Wonderful.