Why does it matter if i don't want to get married.....?

When people ask me whether i want to get married and i reply "Not really my thing" or "No, i don't see the point in it" people always turn to me as if i'm crazy or something. Why do people have to get married these days? Why is it that important? Cavemen & cave women back in the stone age didn't get married, so why should humans today? I'm not saying that i want to live the bachelor life, but i would rather be with a girl and then if anything goes wrong there is no messy divorce or anything.