I think it depends very much who you have on your friends list, as to whether you want to post personal things like that.
I did post that someone close to me had died. I have friends on there that I wouldn't ever meet up with one to one (I don't have many friends at all that are really close, sadly). These are people that I do hobby groups with, that I'm friendly with etc, but that I don't know really well. They would have noticed that I was away from the groups for a while, perhaps that I was travelling for the funeral, that I might have been quiet or not up for the social aspects of the groups for a bit, etc. I wanted to spare them the awkwardness when you have friendly conversations with someone that you see regularly but don't know hugely well "oh you've just been away, how lovely, hope you had a super time." "actually it was a funeral of close relative". "oh." awkward pause. Or a casual "oh you've not been for a drink for a couple of weeks, sure you'll come tonight hey? oh go on, why not?" "oh.". more awkwardness. You know, times when you are just have lighthearted small talk and chat, and you don't want to kill the moment by announcing it. Or, times when you know you really don't want to talk about it in front of/with those people, and yet at the same time, it will end up coming out somehow, so better to get the news-giving bit over with in advance on something like facebook, so the news is public, other people know that it's public and they can tell someone who doesn't know if they want. And then if they do say anything to you directly, it's over fairly quickly, you aren't pressed to do things ,and you can control the conversation a bit more.
I don't think anyone should be chided for whether they do or don't post on FB. It's totally up to them and has no bearing on how much you cared for the person. I find it useful as an information service for people I see regularly, and to potentially connect to people who I dont' see regularly but might care about me.
I'm sorry for your loss.