1) Chili is a dish most closely associated with the southwestern United States.
2) Among the most important cultivars of that region, dating back thousands of years, are: peppers, maize, squash, beans. This combination provides a complete mix of nutrients for a healthy diet.
3) Therefore, adding all those ingredients to chili in some form or other is entirely justifiable, as well as being historically accurate.
Meat, on the other hand, is entirely optional.