I would highly recommend you go. It's pretty fun getting to meet everyone else in your course and there's a few enjoyable activities. There will be some important information covered such as the course structure and who to contact in case of xyz. You can also attend the on campus events but the majority of high school leavers won't be there as they would have done it at ocamp.
Another advantage is that you'll get to know quite a few people before you actually start uni. This can help with when you do groupwork in tutorials in the first few weeks because you'll all know each other. Plus it's pretty cheap for a camp.
Is there any reason in particular that you don't want to go? A few of us have been to ocamp before and can help answer any questions you might have on it.