What was the necessity for the entire procedure of ritual slaughter? For the sake of self discipline. It is far more appropriate for man not to eat meat; only if he has a strong desire for meat does the Torah permit it, and even this only after the trouble and inconvenience necessary to satisfy his desire. Perhaps because of the bother and annoyance of the whole procedure, he will be restrained from such a strong and uncontrollable desire for meat.
Keli Yekar, quoted in Abraham Chill, The Mitzvot: The Commandments and Their Rationale (New York: Bloch, 1974), p. 400; as quoted in Richard H. Schwartz, Judaism and Vegetarianism (New York: Lantern Books, 2001), p. 11.