Howcome some friends only show their username and not full name as well?

[Nicole]

Some of my snapchat friends only show their username, while others show their full name in bold then their username underneith. Why is that?
I was thinking it had to do with whether or not they are in my contacts. So if they are their full name will show up. But then i realized there were some people that only had their username that were in my contacts, so then i was thinking maybe they don't have their mobile # attached to their username so then their full name wont show up?

[Walter]

They choose to do so.

Maybe for privacy.