Why do people delete those Facebook friends they've not heard from lately?

I wonder if it’s some FB unspoken rule/fad/cultural thing to do that, or if the reasons vary from person to person. :/

They’ve either decide that they don’t care about the people any more or that those people don’t care about them.

I find it a foolish bid for attention. Many people don’t post on Facebook, or they don’t even log on. Yet, when someone posts “I’m going to clear out my friends list” then everyone says “don’t delete me!” You know what? Clear it out if you want to clear it out, don’t announce it. Furthermore, if you want to hide something from someone, you can do so without unfriending them.

Edit: decided

In the early days of Facebook people were adding everyone they knew or came across and then later on you are having to sift through a ton of new posts from people you really have little to no interest in and don’t communicate with gets them weeded off the friends list.

My friend and I were discussing, only today, how much we hate people announcing of Facebook that they’re having a friend clear out. Attention seeking as far as I’m concerned!

Yeah, I have had several people say that they were doing that. Some wanted me to let them know if I did not want to be deleted, others just cleaned up how they wanted and who they wanted. I never responded to those who asked.
I don’t understand it. It doesn’t cost anything to keep those on the list although early on I did have to block some folks because I really did not need to know they were going to the bathroom now, nor when they came back from the bathroom and truly did not need to know how it went. Just let me know in general terms how you are, what you are thinking, etc. not a minute by minute update. Oh, and I blocked some chronic whiners too.