I get this question often. There's lots of good reasons to be vegan. In honour of World Vegan Day (November 1st) here are my top 5:
image courtesy of Snooters Farm Animal Sanctuary
1 - It's more environmentally friendly. Saves trees, uses less water (More than half of all water used in the U.S. is used to raise and kill animals for the table), less fossil fuels (Producing just one hamburger uses enough fossil fuel to drive a small car 20 miles), creates less pollution (animal feces is a major contributor to global warming and acid rain, plus pollutes numerous rivers and water sheds annually), the worlds 17 major fisheries are at the point of collapse because of over fishing.

2 - It's the most compassionate way to live. Animals feel pain. Modern agriculture keeps cows, calves, pigs, chickens, turkeys, ducks, and other animals in small overcrowded sheds, stalls, cages, or crates, where they're often unable even to turn around. These intelligent, social animals are deprived of veterinary care, exercise, sunlight--even the feel of grass under their feet. What we eat means choosing between the horrors of factory farming and respect for another sentient being.

3 - It's healthier. Vegans have lower rates of obesity, coronary heart disease, high blood pressure, large bowel disorders, cancers and gallstones. Not to mention the hormones and antibiotics used in raising animals

4 - It feeds more people. Seven kilograms of grain are required to produce 1 kilogram of beef; the conversion is 4-to-1 for pork and 2-to-1 for poultry. Each kilogram of meat represents several kilograms of grain that could be consumed directly by humans, not to mention the water and farmland required to grow the grain. To put this in uncomplicated terms, the beef in a Big Mac represents enough wheat to produce five loaves of bread.

5 - It tastes good.

The greatness of a nation & its moral progress can be judged by the way we treat animals
- Gandhi