Well, so there are two approaches:

- some see no reason to hide it

- some see no reason to show it

The norm in life is to not know who people’s friends are. People don’t walk around with images of their friends on their forehead. Social media has normalized oversharing.

We tend to hide precious and invaluable things from others. Maybe, they look at their friends in that way. 

I hide my friend's list. I'm very active in the forum and if I allow private messages from strangers, I receive a lot of messages by scammers, flirters and other intrusive people. I don't want them to bother my friends.