How about "marriage is an antiquated institution and I don't see the need for it?" How about "if I do get married, the only difference in our relationship will be that we threw a bit party for all our friends and family, and maybe went on a trip together afterwards, and since we're poor students, who are broke as f***, that isn't likely to happen any time soon".
Says who? Your marriage is what you make it and no one else defines it but you. It's only an antiquated institution if you choose to make it so. As for spending bajillions of dollars for a piece of paper, that's a wedding, which in my opinion has very little (if anything) to do with marriage. When we got married, all that mattered to us was taking the time to say to each other in our own words why we wanted to spend the rest of our lives together and making special promises that held personal meaning for us, with the people who mattered most in our lives there to share that day with us - and you can do that for less than it costs to fill your tank with gas.
I think people are getting caught up in the terminology here, rather than the strength of the relationship and the commitment between two people. If you pledge your life to someone, are bonded in every way, and know to yourself the strength of your relationship, then in my books you're "married" paper wedding or not, and would deserve the accorded respect. By the same token, lots of people who are legally "married" don't have a relationship worth a crap and I wouldn't take them any more seriously than a sandbox relationship at playschool.
There are slackers in both categories...some people who are legally married aren't worth any more than the paper they signed, and some people who are commonlaw really just want free milk without buying the cow. If you know you don't fall into either category, then why get upset? Just say "they're not talking about me" n move on.