why do y/h users keep their Q&A private. Like... most of the Q&A is pretty low intellectual stuff?

Not all users keep their activity private, but many do.

Me personally, since I started on the site I've heard so much about the people who will go through one's Q&A with a fine tooth comb looking for stuff to report, or how people will falsely report all of your Q&A whether or not they are actual violations (sometimes with multiple accounts), that I've always had my Q&A private.

And my network is not something I feel a need to share either. I have added some users, these people can look at my Q&A as much as they want, as I'm fairly confident these users would not abuse that ability.

As the others have said, it's to avoid nuisance reporters. Even though you can get some stuff back on appeal if if it was found that there was no valid reason for being reported it's a lot of hassle so I just decided to close my network, except to my contacts.

After losing around 4 accounts to trolls & hackers I got wise & closed mine to everyone,even contacts.Two were level 6 & 7 and that hurts,let me assure you.This one was suspended but I got it back on appeal.I now change my password every few days to further protect it.

Quite simply to avoid trolls and stalkers who report most anything.

to keeep from needless reporting from trolls and others