You don't have to, most are a pain in the ***, others make the best moments of your life. Until you find something that feels right you just haven't found the one.
Could be a lack of maturity thing. Like the person before me said, you don't NEED to take relationships seriously. You should just know that you may be doing a great deal of emotional damage to the other person. There is nothing more humiliating in this world than to invest yourself into someone else and have them crap all over you.