Why would you think about whether it was relevant in 5 years? I've literally never cared or thought about that when sending those kinds of messages. It's just a basic picture, not sexting or something else potentially sensitive.

I don't understand why I should force everyone I know to install yet another random social media app when a regular message works just fine.

Ok, we understand that you don't get it but what's with the tone where you're basically disputing Snapchat's success? This is a popular way of communicating these days. Deal with it. Snapchat is the only social media I've ever shared anything on. For me it's revolutionary.