I screenshot and save just about every Snapchat between my girlfriend and I. A lot of them are great pictures of our dogs, memories from vacations, a lot of junk but sentimental junk. At least have a feature to save your own waves, then maybe something enabled to allow your friends to save your waves. Maybe your friend tells a great story, you save it, they pass away, what a great memory to have of someone.

Edit: Just downloaded it and see that you can save waves. Nice.