It's important to get an annual check up because, it's important to make sure you are okay and your not having something internal going on.
If you don't go to the doctor, you might become very sick and may not be able to get over it that quickly. Which is something that need's to be evaluated by a doctor.
Going to a doctor yearly is a great way to make sure there's nothing going on. Not going to the doctor is a big risk to be taking. It's very important you go see a doctor yearly.