As a vegetarian you are still consuming dairy products, eggs, etc.
Dairy is not healthy for the human body. Milk is meant for baby cows to grow up and become an adult cow that weighs hundreds of kilograms. Do you think it's healthy for us to consume something that makes a cow grow so fast? Milk has so many hormones in it that are not good for humans. Dairy causes acne. Also milk contains puss, yum!
Eggs contain a lot of cholesterol which is not good for humans. (Also an egg is a chicken's period! Why would you want to eat that?!)
Eating a plant based diet has been scientifically proven to be the best diet for the human body, it can even reverse heart disease! Check nutritionfacts.Org for more information. :)