Why wont my parents let me have a girlfriend anymore?

ok well ive had two "real" girlfriends. my parents let me date both of them and everything. well i just broke up with one and now they say i cant take another girl to the soccer banquet and i cant have another girlfriend until i become mature..their reason was that all it ends up at this age is somebody getting hurt but nothing is going to change when i get older, and im not that young. so i dont know how to convince them to let me have another girlfriend because i think its dumb and unfair because nothing will change somebody getting hurt even when im older.