Is it 'normal' not to mention some ones death after a certain point?

I'm just confused like usual right now, with 'how things work'
I just realize , no one on my 'in real life friends' posted or talked about our friend last week (fb is my connection with them all). It was back in 2009, .... I haven't forgotten, I still miss him.
I mentioned him in a post on fb, guess I'm the odd one?
Sigh, I am sure I'm not the only one that remembers, and I realize I'm the touchy one with 'not suppose to talk about it?' And getting upset about that 'don't talk about it' style.
I just don't understand I guess, ...