Not if you really don't want to. Of course, there are repercussions to your actions. If you're living in their home, they could always kick you and stop feeding you or giving you money since you want do things on your own.
At age 18 you are legally an adult, and your parents can't force you to do anything. Of course, if you are still living there your parents can kick you out at any time for disobeying them. It's your choice really!
To the extent that you accept their financial support, accept their rules. Don't like their rules? Get your own place, provide your own support. You're eighteen, you are allowed to do that. If you are financially unable to do that, follow your parents rules until you can do that. Even if those rules seem to strict.
The real question is, can you leave and support yourself? If you leave just because of a dispute or a disagreement with your parents, you may not be prepared to go out into the real world. What of you leave and then realize that you want to go back (what if). Akwarrrrd.