Private profiles
If someone has a profile that's completely private, I would reject. My profile is open and I have my profile picture public. But the rest of my pics are for certified friends only. Not because I am prude or shy. It's because of the many lurkers who are not really nudists..
There is one situation when I might accept a friend request from someone with a private profile and that is if they had posted something that I really found interesting to a group, or made some effort to introduce themselves extensively in a message . Otherwise I would not only decline, I would block. Blocking is the solution for lurkers.
I reject requests from private profiles. When I get a friend request, I look over the profile. If I find a common interest then I'll accept. I'm not in the habit of "collecting" friends. That is a problem with Social Media of all type today. The idea that the more friends, followers etc. you have, the more popular you feel. I guess I'm too old for that kind of rubbish. Incidentally a friend request from a certified user is more likely to be accepted by me.