There are over 12 million vegetarians in the US alone. There are many surprising health benefits to being vegetarian that many people are not aware of. Also an animal at the top of the food chain eats all of the toxic substances found in their prey and their prey's prey and so on. Nearly all of these toxic substances are related to the excessive use of pesticides, and insecticides and petrochemical fertilizers used on croplands. The environmental defense fund estimates that the average American has 1.5 grams of DDT in their body.
Some people become vegetarian for environmental reasons.
Over fishing causes the needless deaths of over 200 thousand marine mammals and birds caught in nets each year. Many species of fish are becoming extinct. Agricultural engineers have compared the energy of producing pork, poultry and other meats to the cost of producing various plant foods. They discovered that the least efficient plant food was 10 times as efficient as the most efficient animal food. It takes one gallon of gasoline to produce one pound of grain-fed beef.