No. You don't have to host someone. If you don't want to host, simply edit your profile and change your hosting status to "Can't host". If you change your status to "Can't host" no one will be able to send you a hosting request. You can change your status at any time and as frequently as you want.
It is recommended that someday you consider opening up your home to hosting, as soon as you are comfortable and your life situation allows.