Looking for insight on my boyfriend's attitude toward marriage?

My boyfriend and I have been together for well over 2 years now. We went through a bit of a rough patch, but overall our relationship is great. I love him very much and couldn’t imagine my life without him – I think he’d say the same. He’s always been really iffy about the idea of marriage around me. He says you don’t need to get married, it’s just a piece of paper, blah blah blah. Whenever he talks about his future around me, he makes sure not to include me in it. For example, he’ll say “If I ever grow old with someone…” or “If I was to get married, me and my wife…” It seems like he’s afraid to give me the idea of us spending the rest of our lives together. He likes to avoid the topic completely. HOWEVER… there have been times where he’s said things (usually after having a few drinks) that tell me that he really does want to get married and that he does plan on being with me. A few people have also told me this – both my mom and my cousin have told me that they get the feeling he’d propose soon because of hints he’s dropped to them. Apparently he’s fine to talk about it when I am not around. But I’m not sure what to believe. Why is he like this?