You've probably asked yourself that one at one point in your life. As someone who's been a vegetarian for several years, as well as learned from world-class chefs and dietitians, there are several of valid reasons to make a fresh start and begin a plant-based diet.
A lot of people concerned about their well-being are searching for ways to get rid of unhealthy eating habits. By taking meat out of your diet, you are getting rid of a major source of saturated fat, cholesterol, and various other harmful elements. This doesn't include the chemicals that you take in by having meat in your diet. The animal processing industry uses various growth hormones, antibiotics, and other unnatural chemicals that you will wind up eating and processing through your body.
You can also take into account the environmental aspects. Research has proven that the level of harmful gases given off from the daily excrement of millions of factory-raised livestock is more harmful to the world than every car put together. Additionally, the dizzying amounts of feed necessary to feed the millions of head of livestock requires additional millions of pounds of pesticide and other chemicals, which can run off into drinking water.
One more element of the discussion over going vegetarian has to do with the less-than-humane ways animals are processed for eating. We like to think that chickens, pigs, cows, etc. that are raised for consumption lead pleasant lives, similar to how we treat our dogs and cats.
But the hard fact is that the majority of livestock are looked at as commodities and are treated as nothing more than a product; not sentient creatures. Realize that most livestock live in small boxes, often not allowed room to stand. They suffer from awful diseases and are kept viable so that they can make it to the slaughterhouse, where they are shocked, hit with electric bolt guns, have their throats slit, and some are even dumped into scalding water while still conscious.
The good news is that you can lead a healthy, ethical life by eating a meatless diet. Vegetarians often have lower incidences of disease, and several report feeling a higher level of focus and concentration all through the day.