Sad? I think Snapchat manages to be successful because the messages are not meaningless just because they are later removed, but because they are as meaningful and easily relatable as normal conversations. If you aren't around to hear the latest gossip (Snapchat story), you will miss out. But it doesn't matter, because it's not about life or death. Not something even intended to be saved, catalogued, scrutinized. And for direct messages, they will go away as soon as they are read or seen. Just like in real life. They don't stick around, hovering around for retrieval months later. I think this reduces the cognitive load and makes it easier for people to share what they would be able to share in real life.