Why are there so many varieties of Buddhism is a good and honest question. Basically, it's because Buddhism is a living organism which adapts to time, culture, and social needs. Here's how Buddhist author Pat Allwright explains it: "The teachings (of the Buddha) were added to or modified, according to the culture and understanding of the people. This is only natural since Buddhism is not a religion of dogma, but of action. It is a practical philosophy which relates to the time and place."