Ok Rick, you asked twice!
I'm a vegetarian because I don't need meat.
Nor does anyone else, but it might not be a good enough reason for you. Thats OK by me.
We can store carbohydrates and fats in our bodies from one day (or year) to the next. Protein is different. It cannot be stored, so any we eat over and above our daily requirement is actually a problem for our body. The liver converts the excess amino acids to urea which is excreted by the kidneys. To put it briefly, most of the steak goes down the toilet!
Finally the field that feeds one cow could feed ten people with a crop of beans or cereals. In a world where many people simply don't have enough to eat, that must also be a consideration.
Sorry to sound pompous but its how I fee!