another commitment phobic guy

I currently live with my bf of 4 yrs. Life is good, we get along wonderfully and care about each other. He just has an incredibly huge fear of commitment. We have never defined our relationship, or discussed that we wouldnt see other people, that is just pretty much how it is. Now that all of his friends are getting married and engaged this year, he has become quite stressed and continually tells me how much he does not understand why people get married and why it is a big deal. He feels that if 2 ppl are in love and want to spend their lives together, they should just do it and he doesnt "get" why people have to get married. I explain to him my view and told him this is one thing he wont change my mind about (I think he thought I would cave on the issue or something). I told him if that is how he truly feels then we both need to move on with our lives b/c that is not what I want. I know that he is the man I could spend the rest of my life with, I know that we would have a wonderful life. I dont understand why this marriage thing is such a problem for him. I am almost 30, and have been living status quo for 4 yrs, and I truly cant hold out for him indefinitely. I know that means letting him go and as rough as that is, I will have to do that if he doesnt step up. I jsut dont want him to do it to shut me up. I dont understand what the problem is. Is anyone in this situation or have any insight? he keeps asking why marriage is so important. I see it as giving of yourself, total commitment, sharing life, the place where 2 lives become one together forever. I guess I just dont get it.

All I know is, my sister's friend was in the same situation, except that it had been 6 years, and she was older than you. She gave him an ultimatum. It sounded crazy to me, but it worked, and now years later they're happily married with kids. I'm not saying this will always happen, but the way I see it, the wedding is just one day out of your life, and the next day you guys will just be back to your normal old life living together! Maybe if you try to help him see it that way, or let him know you don't mind if HE views it that way, because after all he's going to love you the same whether you're married or not.