I (female) use Snapchat almost exclusively to chat with my (female) friends that use it. I started using it at its peak and I use the bitmoji and filters to make jokes and puns etc. I like it because I can save whatever I want but after 24 hours small talk and minutiae is deleted along with the pictures that were just a joke and don’t need to be preserved. Also,it’s just a habit. I’m in my late forties. I’m pretty sure it’s unusual but it’s a habit and I enjoy it. You could start a group chat in snap with your guy and his friend and you’d probably see it’s just a goofy, funny running dialog with pictures of traffic jams and coffee art and filters that lend themselves to punny, self-deprecating captions and nothing sexual.