Well, I can only speak from my personal experience of course. I've been together with my bf for 9 years and we're still not engaged. It's not that we are afraid of settling down together, because we've already pretty much done that. We have lived together for years, we have a joint bank account, we make plans about the future, etc. All the things that marriage usually entails but we're not actually married. Both of us are not huge proponents of marriage, but I could see us getting married one day. At the moment I guess I just don't see the need for it and I don't think it would actually change our relationship, besides having a ceremony to formalize it. But I already feel like I am married, in a way.
However, it seems like marriage is something that is really important to you. Can I ask how old you are? It's ok to wait a bit if you're still young, even if you are living together with your bf. Weddings are expensive as well, maybe he wants to save up some more money as well to afford a nice wedding for you both.
I don't think it's good to pressure your bf into getting married to you if he's not ready, but ultimately you will have to find out why he is hesitant about maybe getting engaged. I would just talk to him about it, explain that this is something you really want, you want to get married to him, not just because all your friends are getting married.
People often as me and my bf when we're getting married, but I don't let it get to me. We will do it on our own time, when we feel ready.